<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with Wdesk from Workiva-->
<!--Copyright 2021 Workiva-->
<!--r:e9028174-de97-4dfb-a57b-8c0ddf1ca4e1,g:e830226d-15cb-4e59-abe4-e90df9aedcef-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/Coverpage" xlink:type="simple" xlink:href="anab-20201231.xsd#Coverpage"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/Coverpage" xlink:type="extended" id="ieb956bf8a2ea4da096cc52acf79d30f6_Coverpage"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/ConsolidatedBalanceSheets" xlink:type="simple" xlink:href="anab-20201231.xsd#ConsolidatedBalanceSheets"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/ConsolidatedBalanceSheets" xlink:type="extended" id="iafd6bc71d89945c799a1168390c251e9_ConsolidatedBalanceSheets"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/ConsolidatedBalanceSheetsParenthetical" xlink:type="simple" xlink:href="anab-20201231.xsd#ConsolidatedBalanceSheetsParenthetical"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/ConsolidatedBalanceSheetsParenthetical" xlink:type="extended" id="ie95da546021f42cc8be795e8e08e43c2_ConsolidatedBalanceSheetsParenthetical"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/ConsolidatedStatementsofOperationsandComprehensiveLoss" xlink:type="simple" xlink:href="anab-20201231.xsd#ConsolidatedStatementsofOperationsandComprehensiveLoss"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/ConsolidatedStatementsofOperationsandComprehensiveLoss" xlink:type="extended" id="i49ff747fbfaf4475a205b1838e0d1c30_ConsolidatedStatementsofOperationsandComprehensiveLoss"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/ConsolidatedStatementsofOperationsandComprehensiveLossParenthetical" xlink:type="simple" xlink:href="anab-20201231.xsd#ConsolidatedStatementsofOperationsandComprehensiveLossParenthetical"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/ConsolidatedStatementsofOperationsandComprehensiveLossParenthetical" xlink:type="extended" id="i04bb3d86930f4744a458c7a7895fd3e9_ConsolidatedStatementsofOperationsandComprehensiveLossParenthetical"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/ConsolidatedStatementsofStockholdersEquity" xlink:type="simple" xlink:href="anab-20201231.xsd#ConsolidatedStatementsofStockholdersEquity"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/ConsolidatedStatementsofStockholdersEquity" xlink:type="extended" id="i379e841036ee4bd39ab2d7ae333eccd2_ConsolidatedStatementsofStockholdersEquity">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_679fa31e-a6ba-4d3d-859d-c84bde60da9b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_012ee252-2e34-470e-a2b4-c9146da2a307" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_679fa31e-a6ba-4d3d-859d-c84bde60da9b" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_012ee252-2e34-470e-a2b4-c9146da2a307" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesOutstanding_724e956e-5b3a-4fc6-af97-c9180102a274" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_012ee252-2e34-470e-a2b4-c9146da2a307" xlink:to="loc_us-gaap_SharesOutstanding_724e956e-5b3a-4fc6-af97-c9180102a274" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_73326159-3d2b-4afb-b00c-5b93f5b5c3f5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_012ee252-2e34-470e-a2b4-c9146da2a307" xlink:to="loc_us-gaap_StockholdersEquity_73326159-3d2b-4afb-b00c-5b93f5b5c3f5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_2d340808-3709-4b76-b698-bac70e55ccdf" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_012ee252-2e34-470e-a2b4-c9146da2a307" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_2d340808-3709-4b76-b698-bac70e55ccdf" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_550b5351-fb42-4d69-abde-23eb96bc8dc0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_012ee252-2e34-470e-a2b4-c9146da2a307" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_550b5351-fb42-4d69-abde-23eb96bc8dc0" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalStockIssuedIssuanceCosts_8db3bae5-1b23-483a-a0d4-e01780e4e4a6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalStockIssuedIssuanceCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_012ee252-2e34-470e-a2b4-c9146da2a307" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalStockIssuedIssuanceCosts_8db3bae5-1b23-483a-a0d4-e01780e4e4a6" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_9857460d-a8c5-4ce6-b108-83a859a967ce" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_012ee252-2e34-470e-a2b4-c9146da2a307" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_9857460d-a8c5-4ce6-b108-83a859a967ce" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_a78af49a-4840-43a3-a31d-19bf03da7118" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_012ee252-2e34-470e-a2b4-c9146da2a307" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_a78af49a-4840-43a3-a31d-19bf03da7118" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_StockIssuedDuringPeriodSharesDueToWarrantsExercised_2a257e03-ab33-4b8e-b073-c17fdc68690a" xlink:href="anab-20201231.xsd#anab_StockIssuedDuringPeriodSharesDueToWarrantsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_012ee252-2e34-470e-a2b4-c9146da2a307" xlink:to="loc_anab_StockIssuedDuringPeriodSharesDueToWarrantsExercised_2a257e03-ab33-4b8e-b073-c17fdc68690a" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_StockIssuedDuringPeriodValueDueToWarrantsExercised_6b88b497-9882-4bd0-bebb-2abe2101eccc" xlink:href="anab-20201231.xsd#anab_StockIssuedDuringPeriodValueDueToWarrantsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_012ee252-2e34-470e-a2b4-c9146da2a307" xlink:to="loc_anab_StockIssuedDuringPeriodValueDueToWarrantsExercised_6b88b497-9882-4bd0-bebb-2abe2101eccc" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationStockOptionsRequisiteServicePeriodRecognition_72562285-d726-4967-a04a-a4cb6cc1d062" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationStockOptionsRequisiteServicePeriodRecognition"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_012ee252-2e34-470e-a2b4-c9146da2a307" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationStockOptionsRequisiteServicePeriodRecognition_72562285-d726-4967-a04a-a4cb6cc1d062" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_180af801-0530-412b-8d1b-dd51a0f8da7f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_012ee252-2e34-470e-a2b4-c9146da2a307" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_180af801-0530-412b-8d1b-dd51a0f8da7f" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_a4bf2ca4-2764-4091-bee4-c23048985a71" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_012ee252-2e34-470e-a2b4-c9146da2a307" xlink:to="loc_us-gaap_NetIncomeLoss_a4bf2ca4-2764-4091-bee4-c23048985a71" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesOutstanding_264ef90d-c748-4a62-80ba-7d0f38cde2bf" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_4dd97ded-6b6e-4d1b-9de8-6214409abf54" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_c16160cf-5f3e-4645-8be8-f7fd60a803f8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_679fa31e-a6ba-4d3d-859d-c84bde60da9b" xlink:to="loc_us-gaap_StatementTable_c16160cf-5f3e-4645-8be8-f7fd60a803f8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_c8308cfe-c3db-487d-a938-7f5fb44fe580" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_c16160cf-5f3e-4645-8be8-f7fd60a803f8" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_c8308cfe-c3db-487d-a938-7f5fb44fe580" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_c8308cfe-c3db-487d-a938-7f5fb44fe580_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_c8308cfe-c3db-487d-a938-7f5fb44fe580" xlink:to="loc_us-gaap_EquityComponentDomain_c8308cfe-c3db-487d-a938-7f5fb44fe580_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_2f68d97a-3544-4e2d-a2dc-37a3c1fb0263" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_c8308cfe-c3db-487d-a938-7f5fb44fe580" xlink:to="loc_us-gaap_EquityComponentDomain_2f68d97a-3544-4e2d-a2dc-37a3c1fb0263" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_ee84f0bb-1f64-4f2d-bd98-35d39a3a646c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_2f68d97a-3544-4e2d-a2dc-37a3c1fb0263" xlink:to="loc_us-gaap_CommonStockMember_ee84f0bb-1f64-4f2d-bd98-35d39a3a646c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_a0f0d11b-5c67-4c8c-8a30-5adb3853b159" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_2f68d97a-3544-4e2d-a2dc-37a3c1fb0263" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_a0f0d11b-5c67-4c8c-8a30-5adb3853b159" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_314da7ad-4fe1-4c9b-869a-ed0db7df9e80" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_2f68d97a-3544-4e2d-a2dc-37a3c1fb0263" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_314da7ad-4fe1-4c9b-869a-ed0db7df9e80" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_6c94e57d-0d3f-44fa-bad0-b83ce5b85587" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_2f68d97a-3544-4e2d-a2dc-37a3c1fb0263" xlink:to="loc_us-gaap_RetainedEarningsMember_6c94e57d-0d3f-44fa-bad0-b83ce5b85587" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/ConsolidatedStatementsofCashFlows" xlink:type="simple" xlink:href="anab-20201231.xsd#ConsolidatedStatementsofCashFlows"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/ConsolidatedStatementsofCashFlows" xlink:type="extended" id="i3b54ae1271f04c24ae2a3502585aca70_ConsolidatedStatementsofCashFlows"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/DescriptionoftheBusiness" xlink:type="simple" xlink:href="anab-20201231.xsd#DescriptionoftheBusiness"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/DescriptionoftheBusiness" xlink:type="extended" id="i07cc3fa2bc7c4c01aa3be3b426feb6e7_DescriptionoftheBusiness"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/DescriptionoftheBusinessDetails" xlink:type="simple" xlink:href="anab-20201231.xsd#DescriptionoftheBusinessDetails"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/DescriptionoftheBusinessDetails" xlink:type="extended" id="iccdbce73426947538b6f38882812456c_DescriptionoftheBusinessDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightLineItems_9138f0c0-687c-4b7b-9e0d-bca0241d362a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ClassOfWarrantOrRightLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_4c495b3c-eb50-4624-9507-a7452a108cfe" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_9138f0c0-687c-4b7b-9e0d-bca0241d362a" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_4c495b3c-eb50-4624-9507-a7452a108cfe" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesIssuedPricePerShare_68a8075b-c50d-446d-91f0-37fbd0e98b7a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SharesIssuedPricePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_9138f0c0-687c-4b7b-9e0d-bca0241d362a" xlink:to="loc_us-gaap_SharesIssuedPricePerShare_68a8075b-c50d-446d-91f0-37fbd0e98b7a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfCommonStock_5f6a58bf-92fd-4633-9d34-35a23b416971" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromIssuanceOfCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_9138f0c0-687c-4b7b-9e0d-bca0241d362a" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfCommonStock_5f6a58bf-92fd-4633-9d34-35a23b416971" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightTable_32e10816-809c-4295-ba38-e0b29f8a9a17" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ClassOfWarrantOrRightTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_9138f0c0-687c-4b7b-9e0d-bca0241d362a" xlink:to="loc_us-gaap_ClassOfWarrantOrRightTable_32e10816-809c-4295-ba38-e0b29f8a9a17" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_48b87fbc-48b0-48cf-ae65-0152442e21c3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsidiarySaleOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ClassOfWarrantOrRightTable_32e10816-809c-4295-ba38-e0b29f8a9a17" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_48b87fbc-48b0-48cf-ae65-0152442e21c3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_48b87fbc-48b0-48cf-ae65-0152442e21c3_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_48b87fbc-48b0-48cf-ae65-0152442e21c3" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_48b87fbc-48b0-48cf-ae65-0152442e21c3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_fdf0177b-e8ea-4d72-a1e3-afe51e122319" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_48b87fbc-48b0-48cf-ae65-0152442e21c3" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_fdf0177b-e8ea-4d72-a1e3-afe51e122319" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OverAllotmentOptionMember_f424fb18-6330-4a3f-ad85-2ca3b1108253" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OverAllotmentOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_fdf0177b-e8ea-4d72-a1e3-afe51e122319" xlink:to="loc_us-gaap_OverAllotmentOptionMember_f424fb18-6330-4a3f-ad85-2ca3b1108253" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/SummaryofSignificantAccountingPolicies" xlink:type="simple" xlink:href="anab-20201231.xsd#SummaryofSignificantAccountingPolicies"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/SummaryofSignificantAccountingPolicies" xlink:type="extended" id="ic43b4179dff64e6fb7988e864e0e434c_SummaryofSignificantAccountingPolicies"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/SummaryofSignificantAccountingPoliciesPolicies" xlink:type="simple" xlink:href="anab-20201231.xsd#SummaryofSignificantAccountingPoliciesPolicies"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/SummaryofSignificantAccountingPoliciesPolicies" xlink:type="extended" id="if8f01d84050d41b89118b8c5dd61155f_SummaryofSignificantAccountingPoliciesPolicies"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/SummaryofSignificantAccountingPoliciesTables" xlink:type="simple" xlink:href="anab-20201231.xsd#SummaryofSignificantAccountingPoliciesTables"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/SummaryofSignificantAccountingPoliciesTables" xlink:type="extended" id="id7bb0f1a5e9941b394fa7f85c227fb2c_SummaryofSignificantAccountingPoliciesTables"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/SummaryofSignificantAccountingPoliciesAdditionalInformationDetails" xlink:type="simple" xlink:href="anab-20201231.xsd#SummaryofSignificantAccountingPoliciesAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/SummaryofSignificantAccountingPoliciesAdditionalInformationDetails" xlink:type="extended" id="id4be826d8fff4ee6bb93bf48a52186dc_SummaryofSignificantAccountingPoliciesAdditionalInformationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_38a7f826-3f72-4ba9-bd2c-8464698dd89e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentUsefulLife_a05c78e3-1a2d-46e1-a99f-c609c485d537" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_38a7f826-3f72-4ba9-bd2c-8464698dd89e" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentUsefulLife_a05c78e3-1a2d-46e1-a99f-c609c485d537" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TangibleAssetImpairmentCharges_802c39f4-7e2f-43b0-b99d-0af9f6408263" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TangibleAssetImpairmentCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_38a7f826-3f72-4ba9-bd2c-8464698dd89e" xlink:to="loc_us-gaap_TangibleAssetImpairmentCharges_802c39f4-7e2f-43b0-b99d-0af9f6408263" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset_dbeede28-4d21-4424-91ad-90b7d914e94d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseRightOfUseAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_38a7f826-3f72-4ba9-bd2c-8464698dd89e" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAsset_dbeede28-4d21-4424-91ad-90b7d914e94d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiability_fe0e5541-3ad6-4b97-b191-095ff7ad3e0e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_38a7f826-3f72-4ba9-bd2c-8464698dd89e" xlink:to="loc_us-gaap_OperatingLeaseLiability_fe0e5541-3ad6-4b97-b191-095ff7ad3e0e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_c4c2e58a-e723-4293-aede-8faf21599850" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_38a7f826-3f72-4ba9-bd2c-8464698dd89e" xlink:to="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_c4c2e58a-e723-4293-aede-8faf21599850" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_80a0c34b-3815-43cb-996f-0fcf17bc7af6" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_c4c2e58a-e723-4293-aede-8faf21599850" xlink:to="loc_srt_RangeAxis_80a0c34b-3815-43cb-996f-0fcf17bc7af6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_80a0c34b-3815-43cb-996f-0fcf17bc7af6_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_80a0c34b-3815-43cb-996f-0fcf17bc7af6" xlink:to="loc_srt_RangeMember_80a0c34b-3815-43cb-996f-0fcf17bc7af6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_ea195463-cdc6-4ec4-bbb7-42cf69a8216f" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_80a0c34b-3815-43cb-996f-0fcf17bc7af6" xlink:to="loc_srt_RangeMember_ea195463-cdc6-4ec4-bbb7-42cf69a8216f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_2f8d973d-86c2-476e-bdae-ed5236a6bdef" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_ea195463-cdc6-4ec4-bbb7-42cf69a8216f" xlink:to="loc_srt_MinimumMember_2f8d973d-86c2-476e-bdae-ed5236a6bdef" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_e3fe2d48-90f4-431a-9ddb-e3599474ff82" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_ea195463-cdc6-4ec4-bbb7-42cf69a8216f" xlink:to="loc_srt_MaximumMember_e3fe2d48-90f4-431a-9ddb-e3599474ff82" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/SummaryofSignificantAccountingPoliciesSummaryofPotentiallyDilutiveSecuritiesDetails" xlink:type="simple" xlink:href="anab-20201231.xsd#SummaryofSignificantAccountingPoliciesSummaryofPotentiallyDilutiveSecuritiesDetails"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/SummaryofSignificantAccountingPoliciesSummaryofPotentiallyDilutiveSecuritiesDetails" xlink:type="extended" id="idca7113ab2814c33a6557346a4085c1c_SummaryofSignificantAccountingPoliciesSummaryofPotentiallyDilutiveSecuritiesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_03940b80-48c0-4011-80c4-63d9e147a53d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_73b413b2-c8c0-4b83-8134-4185f4a33803" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_03940b80-48c0-4011-80c4-63d9e147a53d" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_73b413b2-c8c0-4b83-8134-4185f4a33803" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_de41b815-b9c0-4034-a64d-5f87531cde5e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_03940b80-48c0-4011-80c4-63d9e147a53d" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_de41b815-b9c0-4034-a64d-5f87531cde5e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_6bd76dc3-a032-4caf-aa36-5c8617162267" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_de41b815-b9c0-4034-a64d-5f87531cde5e" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_6bd76dc3-a032-4caf-aa36-5c8617162267" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_6bd76dc3-a032-4caf-aa36-5c8617162267_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_6bd76dc3-a032-4caf-aa36-5c8617162267" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_6bd76dc3-a032-4caf-aa36-5c8617162267_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_ad66d532-3a5b-4596-9b3e-16216e21e906" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_6bd76dc3-a032-4caf-aa36-5c8617162267" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_ad66d532-3a5b-4596-9b3e-16216e21e906" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_27461c72-2fea-4e84-9bf3-c73da61397e0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_ad66d532-3a5b-4596-9b3e-16216e21e906" xlink:to="loc_us-gaap_EmployeeStockOptionMember_27461c72-2fea-4e84-9bf3-c73da61397e0" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/BalanceSheetAccountsandSupplementalDisclosures" xlink:type="simple" xlink:href="anab-20201231.xsd#BalanceSheetAccountsandSupplementalDisclosures"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/BalanceSheetAccountsandSupplementalDisclosures" xlink:type="extended" id="i7d8f40403bd04d0ca1310b9ac48363ac_BalanceSheetAccountsandSupplementalDisclosures"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/BalanceSheetAccountsandSupplementalDisclosuresTables" xlink:type="simple" xlink:href="anab-20201231.xsd#BalanceSheetAccountsandSupplementalDisclosuresTables"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/BalanceSheetAccountsandSupplementalDisclosuresTables" xlink:type="extended" id="ia49620740fc348178d5da03af2d5abad_BalanceSheetAccountsandSupplementalDisclosuresTables"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/BalanceSheetAccountsandSupplementalDisclosuresPropertyandEquipmentDetails" xlink:type="simple" xlink:href="anab-20201231.xsd#BalanceSheetAccountsandSupplementalDisclosuresPropertyandEquipmentDetails"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/BalanceSheetAccountsandSupplementalDisclosuresPropertyandEquipmentDetails" xlink:type="extended" id="ic36e26a04e6a4c82875e207bed9fa911_BalanceSheetAccountsandSupplementalDisclosuresPropertyandEquipmentDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_ae8483b8-ce88-4f37-9de4-414acf7eee3d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_e3dfefe5-db47-431a-ba2e-7e99b70fdfb3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_ae8483b8-ce88-4f37-9de4-414acf7eee3d" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_e3dfefe5-db47-431a-ba2e-7e99b70fdfb3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_3b46a77d-62ab-4ae3-a139-c9f7bfdc8d4e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_ae8483b8-ce88-4f37-9de4-414acf7eee3d" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_3b46a77d-62ab-4ae3-a139-c9f7bfdc8d4e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_a9605d4a-0ac9-45ab-9dcc-fdb9cbcd7132" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_ae8483b8-ce88-4f37-9de4-414acf7eee3d" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_a9605d4a-0ac9-45ab-9dcc-fdb9cbcd7132" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnSaleOfPropertyPlantEquipment_f1a94cac-5800-451f-879d-78864b71a96e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GainLossOnSaleOfPropertyPlantEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_ae8483b8-ce88-4f37-9de4-414acf7eee3d" xlink:to="loc_us-gaap_GainLossOnSaleOfPropertyPlantEquipment_f1a94cac-5800-451f-879d-78864b71a96e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_b7fa44b1-b0d7-4c20-9ba1-006f6379cb6f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_ae8483b8-ce88-4f37-9de4-414acf7eee3d" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_b7fa44b1-b0d7-4c20-9ba1-006f6379cb6f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_38d75455-7560-4acb-841c-cce1a8f25a94" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_b7fa44b1-b0d7-4c20-9ba1-006f6379cb6f" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_38d75455-7560-4acb-841c-cce1a8f25a94" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_38d75455-7560-4acb-841c-cce1a8f25a94_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_38d75455-7560-4acb-841c-cce1a8f25a94" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_38d75455-7560-4acb-841c-cce1a8f25a94_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_15e10ec5-4c89-48e0-9ce3-f531a121811f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_38d75455-7560-4acb-841c-cce1a8f25a94" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_15e10ec5-4c89-48e0-9ce3-f531a121811f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_LaboratoryEquipmentMember_5c8abba9-a408-48e2-ae8d-959fb552210f" xlink:href="anab-20201231.xsd#anab_LaboratoryEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_15e10ec5-4c89-48e0-9ce3-f531a121811f" xlink:to="loc_anab_LaboratoryEquipmentMember_5c8abba9-a408-48e2-ae8d-959fb552210f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OfficeEquipmentMember_da2f6b7c-d8a9-425a-9348-1a2b4fa89ead" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OfficeEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_15e10ec5-4c89-48e0-9ce3-f531a121811f" xlink:to="loc_us-gaap_OfficeEquipmentMember_da2f6b7c-d8a9-425a-9348-1a2b4fa89ead" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeaseholdImprovementsMember_3422e036-0420-499b-9a92-1e1e9ae44dbd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LeaseholdImprovementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_15e10ec5-4c89-48e0-9ce3-f531a121811f" xlink:to="loc_us-gaap_LeaseholdImprovementsMember_3422e036-0420-499b-9a92-1e1e9ae44dbd" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/BalanceSheetAccountsandSupplementalDisclosuresAccruedExpensesDetails" xlink:type="simple" xlink:href="anab-20201231.xsd#BalanceSheetAccountsandSupplementalDisclosuresAccruedExpensesDetails"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/BalanceSheetAccountsandSupplementalDisclosuresAccruedExpensesDetails" xlink:type="extended" id="i58e9ff8407514e15946d4413fe351276_BalanceSheetAccountsandSupplementalDisclosuresAccruedExpensesDetails"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/CollaborativeResearchandDevelopmentAgreements" xlink:type="simple" xlink:href="anab-20201231.xsd#CollaborativeResearchandDevelopmentAgreements"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/CollaborativeResearchandDevelopmentAgreements" xlink:type="extended" id="i89abfe989c2e4364af6daf71bb6f6966_CollaborativeResearchandDevelopmentAgreements"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/CollaborativeResearchandDevelopmentAgreementsTables" xlink:type="simple" xlink:href="anab-20201231.xsd#CollaborativeResearchandDevelopmentAgreementsTables"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/CollaborativeResearchandDevelopmentAgreementsTables" xlink:type="extended" id="i1445cf7ac4db4fbc98e16eb0c4d7d7f8_CollaborativeResearchandDevelopmentAgreementsTables"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/CollaborativeResearchandDevelopmentAgreementsDetails" xlink:type="simple" xlink:href="anab-20201231.xsd#CollaborativeResearchandDevelopmentAgreementsDetails"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/CollaborativeResearchandDevelopmentAgreementsDetails" xlink:type="extended" id="ib29c8262440f435eb5fb8fbc4e47e758_CollaborativeResearchandDevelopmentAgreementsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_94b4f25c-8c64-435a-bd05-52990a429401" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_RevenueRecognitionMultipledeliverableArrangementsUpfrontFeeReceived_bc75898b-6ca4-45b2-8719-3ed7db8f7cf7" xlink:href="anab-20201231.xsd#anab_RevenueRecognitionMultipledeliverableArrangementsUpfrontFeeReceived"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_94b4f25c-8c64-435a-bd05-52990a429401" xlink:to="loc_anab_RevenueRecognitionMultipledeliverableArrangementsUpfrontFeeReceived_bc75898b-6ca4-45b2-8719-3ed7db8f7cf7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_RevenueRecognitionMilestoneMethodNumberOfOutstandingResearchAndDevelopmentTargets_a4fff030-f37d-49f3-877c-606bca93bccb" xlink:href="anab-20201231.xsd#anab_RevenueRecognitionMilestoneMethodNumberOfOutstandingResearchAndDevelopmentTargets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_94b4f25c-8c64-435a-bd05-52990a429401" xlink:to="loc_anab_RevenueRecognitionMilestoneMethodNumberOfOutstandingResearchAndDevelopmentTargets_a4fff030-f37d-49f3-877c-606bca93bccb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_RevenueRecognitionMilestoneMethodContingentUponPreclinicalAndClinicalTrialEvents_3b4a4151-ed0c-43b7-b51d-2984e59ab385" xlink:href="anab-20201231.xsd#anab_RevenueRecognitionMilestoneMethodContingentUponPreclinicalAndClinicalTrialEvents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_94b4f25c-8c64-435a-bd05-52990a429401" xlink:to="loc_anab_RevenueRecognitionMilestoneMethodContingentUponPreclinicalAndClinicalTrialEvents_3b4a4151-ed0c-43b7-b51d-2984e59ab385" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_RevenueRecognitionMilestoneMethodContingentUponCertainUnitedStatesAndEuropeanRegulatorySubmissionsAndApprovals_3f5b7b38-798f-47a2-80fe-ffdd8dcdde66" xlink:href="anab-20201231.xsd#anab_RevenueRecognitionMilestoneMethodContingentUponCertainUnitedStatesAndEuropeanRegulatorySubmissionsAndApprovals"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_94b4f25c-8c64-435a-bd05-52990a429401" xlink:to="loc_anab_RevenueRecognitionMilestoneMethodContingentUponCertainUnitedStatesAndEuropeanRegulatorySubmissionsAndApprovals_3f5b7b38-798f-47a2-80fe-ffdd8dcdde66" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_RevenueRecognitionMilestoneMethodContingentUponAchievementOfSpecifiedLevelsOfWorldwideSales_3864de57-364e-4f21-ae42-6d976b508c3c" xlink:href="anab-20201231.xsd#anab_RevenueRecognitionMilestoneMethodContingentUponAchievementOfSpecifiedLevelsOfWorldwideSales"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_94b4f25c-8c64-435a-bd05-52990a429401" xlink:to="loc_anab_RevenueRecognitionMilestoneMethodContingentUponAchievementOfSpecifiedLevelsOfWorldwideSales_3864de57-364e-4f21-ae42-6d976b508c3c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_RevenueRecognitionMilestoneMethodAgreementTermFollowingFirstCommercialSaleOrExpirationOfTheLastToExpirePatent_1b1744e3-8957-459f-ab7d-6c5b3eb877e5" xlink:href="anab-20201231.xsd#anab_RevenueRecognitionMilestoneMethodAgreementTermFollowingFirstCommercialSaleOrExpirationOfTheLastToExpirePatent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_94b4f25c-8c64-435a-bd05-52990a429401" xlink:to="loc_anab_RevenueRecognitionMilestoneMethodAgreementTermFollowingFirstCommercialSaleOrExpirationOfTheLastToExpirePatent_1b1744e3-8957-459f-ab7d-6c5b3eb877e5" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_RevenueRecognitionMultipleDeliverableArrangementsUpfrontFees_5da0001f-b2b8-48f9-ae19-8459130bc560" xlink:href="anab-20201231.xsd#anab_RevenueRecognitionMultipleDeliverableArrangementsUpfrontFees"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_94b4f25c-8c64-435a-bd05-52990a429401" xlink:to="loc_anab_RevenueRecognitionMultipleDeliverableArrangementsUpfrontFees_5da0001f-b2b8-48f9-ae19-8459130bc560" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_NetSalesRoyaltyPercent_6b066e04-4aae-4ca0-aea4-5654382c5e11" xlink:href="anab-20201231.xsd#anab_NetSalesRoyaltyPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_94b4f25c-8c64-435a-bd05-52990a429401" xlink:to="loc_anab_NetSalesRoyaltyPercent_6b066e04-4aae-4ca0-aea4-5654382c5e11" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_RevenueRecognitionMilestoneMethodMilestonesAchievedDuringThePeriodAmount_b4423bd9-fce2-4148-930a-42083206c2af" xlink:href="anab-20201231.xsd#anab_RevenueRecognitionMilestoneMethodMilestonesAchievedDuringThePeriodAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_94b4f25c-8c64-435a-bd05-52990a429401" xlink:to="loc_anab_RevenueRecognitionMilestoneMethodMilestonesAchievedDuringThePeriodAmount_b4423bd9-fce2-4148-930a-42083206c2af" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_RevenueRecognitionMilestoneMethodNumberOfMilestonesAchievedDuringPeriod_9159351a-8636-4a88-84c7-713482bd627e" xlink:href="anab-20201231.xsd#anab_RevenueRecognitionMilestoneMethodNumberOfMilestonesAchievedDuringPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_94b4f25c-8c64-435a-bd05-52990a429401" xlink:to="loc_anab_RevenueRecognitionMilestoneMethodNumberOfMilestonesAchievedDuringPeriod_9159351a-8636-4a88-84c7-713482bd627e" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_222a4c66-0717-43e3-afc1-237061ac323c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_94b4f25c-8c64-435a-bd05-52990a429401" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_222a4c66-0717-43e3-afc1-237061ac323c" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_RevenueRecognitionMilestoneMethodMaximumRevenuePerMilestone_8ceaef03-7b8d-4960-8b51-1abafc8bbb21" xlink:href="anab-20201231.xsd#anab_RevenueRecognitionMilestoneMethodMaximumRevenuePerMilestone"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_94b4f25c-8c64-435a-bd05-52990a429401" xlink:to="loc_anab_RevenueRecognitionMilestoneMethodMaximumRevenuePerMilestone_8ceaef03-7b8d-4960-8b51-1abafc8bbb21" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_RevenueRecognizedMilestoneMethodMilestonePaymentEarned_abb03463-5a7e-41ae-a817-ea664182b65c" xlink:href="anab-20201231.xsd#anab_RevenueRecognizedMilestoneMethodMilestonePaymentEarned"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_94b4f25c-8c64-435a-bd05-52990a429401" xlink:to="loc_anab_RevenueRecognizedMilestoneMethodMilestonePaymentEarned_abb03463-5a7e-41ae-a817-ea664182b65c" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_10dedad3-36ac-44ba-9a8a-dcfa5d4ad492" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_94b4f25c-8c64-435a-bd05-52990a429401" xlink:to="loc_us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_10dedad3-36ac-44ba-9a8a-dcfa5d4ad492" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_7f08b5f6-a5be-4f00-b7d7-34e1bd68a1e6" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_10dedad3-36ac-44ba-9a8a-dcfa5d4ad492" xlink:to="loc_srt_CounterpartyNameAxis_7f08b5f6-a5be-4f00-b7d7-34e1bd68a1e6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_7f08b5f6-a5be-4f00-b7d7-34e1bd68a1e6_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_7f08b5f6-a5be-4f00-b7d7-34e1bd68a1e6" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_7f08b5f6-a5be-4f00-b7d7-34e1bd68a1e6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_84748d42-691a-4f09-b009-bafa9cbc66d6" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_7f08b5f6-a5be-4f00-b7d7-34e1bd68a1e6" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_84748d42-691a-4f09-b009-bafa9cbc66d6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_TESAROInc.AndTESARODevelopmentInc.Member_b8d45cbb-91c5-4fa1-87d7-8d1941a4417a" xlink:href="anab-20201231.xsd#anab_TESAROInc.AndTESARODevelopmentInc.Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_84748d42-691a-4f09-b009-bafa9cbc66d6" xlink:to="loc_anab_TESAROInc.AndTESARODevelopmentInc.Member_b8d45cbb-91c5-4fa1-87d7-8d1941a4417a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_BristoMeyersSquibbMember_51063180-f3a9-4fcd-a5ac-e000242b61ad" xlink:href="anab-20201231.xsd#anab_BristoMeyersSquibbMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_84748d42-691a-4f09-b009-bafa9cbc66d6" xlink:to="loc_anab_BristoMeyersSquibbMember_51063180-f3a9-4fcd-a5ac-e000242b61ad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfArrangementAxis_6ce7747a-7b43-4a77-81a9-297eee56ca9a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TypeOfArrangementAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_10dedad3-36ac-44ba-9a8a-dcfa5d4ad492" xlink:to="loc_us-gaap_TypeOfArrangementAxis_6ce7747a-7b43-4a77-81a9-297eee56ca9a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_6ce7747a-7b43-4a77-81a9-297eee56ca9a_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ArrangementsAndNonarrangementTransactionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_TypeOfArrangementAxis_6ce7747a-7b43-4a77-81a9-297eee56ca9a" xlink:to="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_6ce7747a-7b43-4a77-81a9-297eee56ca9a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_1c97f240-a7e1-4cc6-9da4-5b5be6c86941" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ArrangementsAndNonarrangementTransactionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_TypeOfArrangementAxis_6ce7747a-7b43-4a77-81a9-297eee56ca9a" xlink:to="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_1c97f240-a7e1-4cc6-9da4-5b5be6c86941" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CollaborativeArrangementMember_214b14e2-5f39-47b0-ae10-8e2c280a102d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CollaborativeArrangementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_1c97f240-a7e1-4cc6-9da4-5b5be6c86941" xlink:to="loc_us-gaap_CollaborativeArrangementMember_214b14e2-5f39-47b0-ae10-8e2c280a102d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_CollaborationAndExclusiveLicenseAgreementMember_6752adbd-b237-4a5c-857c-fbe55c5a5f0b" xlink:href="anab-20201231.xsd#anab_CollaborationAndExclusiveLicenseAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementMember_214b14e2-5f39-47b0-ae10-8e2c280a102d" xlink:to="loc_anab_CollaborationAndExclusiveLicenseAgreementMember_6752adbd-b237-4a5c-857c-fbe55c5a5f0b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_InVivoToxicologyStudiesMember_4dd432fc-26c8-4893-b0ac-a8cd7326e885" xlink:href="anab-20201231.xsd#anab_InVivoToxicologyStudiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementMember_214b14e2-5f39-47b0-ae10-8e2c280a102d" xlink:to="loc_anab_InVivoToxicologyStudiesMember_4dd432fc-26c8-4893-b0ac-a8cd7326e885" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_ClearanceOfInvestigationalNewDrugFromFDAMember_fedcfb85-e40f-4dfc-abab-65b658b9cab7" xlink:href="anab-20201231.xsd#anab_ClearanceOfInvestigationalNewDrugFromFDAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementMember_214b14e2-5f39-47b0-ae10-8e2c280a102d" xlink:to="loc_anab_ClearanceOfInvestigationalNewDrugFromFDAMember_fedcfb85-e40f-4dfc-abab-65b658b9cab7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_Phase2ClinicalTrialInitiationMember_a61d9464-19a3-4328-ba3a-d247cde3dea4" xlink:href="anab-20201231.xsd#anab_Phase2ClinicalTrialInitiationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementMember_214b14e2-5f39-47b0-ae10-8e2c280a102d" xlink:to="loc_anab_Phase2ClinicalTrialInitiationMember_a61d9464-19a3-4328-ba3a-d247cde3dea4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_Phase3ClinicalTrialInitiationMember_c1a8860a-57b7-42a0-b060-f68687ffbe97" xlink:href="anab-20201231.xsd#anab_Phase3ClinicalTrialInitiationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementMember_214b14e2-5f39-47b0-ae10-8e2c280a102d" xlink:to="loc_anab_Phase3ClinicalTrialInitiationMember_c1a8860a-57b7-42a0-b060-f68687ffbe97" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_Phase3clinicaltrialinitiationsecondindicationDomain_5358bc81-87e3-4734-9e0b-87938bf7fd9e" xlink:href="anab-20201231.xsd#anab_Phase3clinicaltrialinitiationsecondindicationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementMember_214b14e2-5f39-47b0-ae10-8e2c280a102d" xlink:to="loc_anab_Phase3clinicaltrialinitiationsecondindicationDomain_5358bc81-87e3-4734-9e0b-87938bf7fd9e" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_FilingOfNDAMember_5a636a35-f19d-4621-85c1-62f3ac265f29" xlink:href="anab-20201231.xsd#anab_FilingOfNDAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementMember_214b14e2-5f39-47b0-ae10-8e2c280a102d" xlink:to="loc_anab_FilingOfNDAMember_5a636a35-f19d-4621-85c1-62f3ac265f29" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_FilingOfMMAMember_c51e5f4a-67dd-49f2-bbb9-6a8164195b25" xlink:href="anab-20201231.xsd#anab_FilingOfMMAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementMember_214b14e2-5f39-47b0-ae10-8e2c280a102d" xlink:to="loc_anab_FilingOfMMAMember_c51e5f4a-67dd-49f2-bbb9-6a8164195b25" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_Phase1ClinicalTrialInitiationMember_15a8e894-d755-499c-8b13-f6f73b88e563" xlink:href="anab-20201231.xsd#anab_Phase1ClinicalTrialInitiationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementMember_214b14e2-5f39-47b0-ae10-8e2c280a102d" xlink:to="loc_anab_Phase1ClinicalTrialInitiationMember_15a8e894-d755-499c-8b13-f6f73b88e563" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_5ccde406-4c42-4619-a1ae-8091ebdc63e8" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_10dedad3-36ac-44ba-9a8a-dcfa5d4ad492" xlink:to="loc_srt_ProductOrServiceAxis_5ccde406-4c42-4619-a1ae-8091ebdc63e8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_5ccde406-4c42-4619-a1ae-8091ebdc63e8_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_5ccde406-4c42-4619-a1ae-8091ebdc63e8" xlink:to="loc_srt_ProductsAndServicesDomain_5ccde406-4c42-4619-a1ae-8091ebdc63e8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_f22a472c-112d-4529-93b5-244bcaabce4d" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_5ccde406-4c42-4619-a1ae-8091ebdc63e8" xlink:to="loc_srt_ProductsAndServicesDomain_f22a472c-112d-4529-93b5-244bcaabce4d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_AnaptysBiogeneratedAntiPD1AntagonistAntibodyTSR042Member_6e5a7ba8-dc86-44d4-8e78-2edf9190bca2" xlink:href="anab-20201231.xsd#anab_AnaptysBiogeneratedAntiPD1AntagonistAntibodyTSR042Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_f22a472c-112d-4529-93b5-244bcaabce4d" xlink:to="loc_anab_AnaptysBiogeneratedAntiPD1AntagonistAntibodyTSR042Member_6e5a7ba8-dc86-44d4-8e78-2edf9190bca2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_AnaptysBioGeneratedAntiTIM3AntagonistAntibodyTSR022Member_74fc21e6-ff41-4e40-960a-741c8d05d7c9" xlink:href="anab-20201231.xsd#anab_AnaptysBioGeneratedAntiTIM3AntagonistAntibodyTSR022Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_f22a472c-112d-4529-93b5-244bcaabce4d" xlink:to="loc_anab_AnaptysBioGeneratedAntiTIM3AntagonistAntibodyTSR022Member_74fc21e6-ff41-4e40-960a-741c8d05d7c9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_AnaptysBioGeneratedAntiLAG3AntagonistAntibodyTSR033Member_8d717386-0f5a-4005-a725-0eb8c889c0ed" xlink:href="anab-20201231.xsd#anab_AnaptysBioGeneratedAntiLAG3AntagonistAntibodyTSR033Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_f22a472c-112d-4529-93b5-244bcaabce4d" xlink:to="loc_anab_AnaptysBioGeneratedAntiLAG3AntagonistAntibodyTSR033Member_8d717386-0f5a-4005-a725-0eb8c889c0ed" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_AnaptysBioGeneratedAntiPD1AntagonistAntibodyCC90006Member_fe8356da-8588-487c-ac98-9e46d04a7ca4" xlink:href="anab-20201231.xsd#anab_AnaptysBioGeneratedAntiPD1AntagonistAntibodyCC90006Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_f22a472c-112d-4529-93b5-244bcaabce4d" xlink:to="loc_anab_AnaptysBioGeneratedAntiPD1AntagonistAntibodyCC90006Member_fe8356da-8588-487c-ac98-9e46d04a7ca4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_5dc4e4bf-ddb6-423c-b146-95179fee0673" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_10dedad3-36ac-44ba-9a8a-dcfa5d4ad492" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_5dc4e4bf-ddb6-423c-b146-95179fee0673" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_5dc4e4bf-ddb6-423c-b146-95179fee0673_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_5dc4e4bf-ddb6-423c-b146-95179fee0673" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_5dc4e4bf-ddb6-423c-b146-95179fee0673_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_02b21b22-857f-47fb-a730-74a151ddcd26" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_5dc4e4bf-ddb6-423c-b146-95179fee0673" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_02b21b22-857f-47fb-a730-74a151ddcd26" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_6821be56-0886-4d33-8c70-c6ffe7b6ace7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_02b21b22-857f-47fb-a730-74a151ddcd26" xlink:to="loc_us-gaap_SubsequentEventMember_6821be56-0886-4d33-8c70-c6ffe7b6ace7" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/NotesPayable" xlink:type="simple" xlink:href="anab-20201231.xsd#NotesPayable"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/NotesPayable" xlink:type="extended" id="ib4dd65bcddfe469aa4f5a9c9cc5ef1ba_NotesPayable"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/NotesPayableDetails" xlink:type="simple" xlink:href="anab-20201231.xsd#NotesPayableDetails"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/NotesPayableDetails" xlink:type="extended" id="ia60ebe0a75204a17a6bd0b1bc85827c8_NotesPayableDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_b21d7f01-b0c6-4510-8846-e4d3d5d2acb0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_DebtInstrumentMaximumBorrowingCapacity_05559902-c47d-48a0-bd1a-bc6fa6e89693" xlink:href="anab-20201231.xsd#anab_DebtInstrumentMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b21d7f01-b0c6-4510-8846-e4d3d5d2acb0" xlink:to="loc_anab_DebtInstrumentMaximumBorrowingCapacity_05559902-c47d-48a0-bd1a-bc6fa6e89693" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_DebtInstrumentNumberOfLoanInstallments_25ef7bce-3e8f-4e0f-9eb7-5964e6433ec8" xlink:href="anab-20201231.xsd#anab_DebtInstrumentNumberOfLoanInstallments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b21d7f01-b0c6-4510-8846-e4d3d5d2acb0" xlink:to="loc_anab_DebtInstrumentNumberOfLoanInstallments_25ef7bce-3e8f-4e0f-9eb7-5964e6433ec8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_99c47f93-cbca-48f6-99ec-32109c226762" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b21d7f01-b0c6-4510-8846-e4d3d5d2acb0" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_99c47f93-cbca-48f6-99ec-32109c226762" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromNotesPayable_1f72874e-9e96-4dee-992c-696b2ddef134" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromNotesPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b21d7f01-b0c6-4510-8846-e4d3d5d2acb0" xlink:to="loc_us-gaap_ProceedsFromNotesPayable_1f72874e-9e96-4dee-992c-696b2ddef134" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_f4df0cfb-0060-4000-9b49-632b90058e0f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b21d7f01-b0c6-4510-8846-e4d3d5d2acb0" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_f4df0cfb-0060-4000-9b49-632b90058e0f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentPeriodicPaymentTermsBalloonPaymentToBePaid_be00de8f-b45d-4815-8fd4-5b09ed8d733b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentPeriodicPaymentTermsBalloonPaymentToBePaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b21d7f01-b0c6-4510-8846-e4d3d5d2acb0" xlink:to="loc_us-gaap_DebtInstrumentPeriodicPaymentTermsBalloonPaymentToBePaid_be00de8f-b45d-4815-8fd4-5b09ed8d733b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_0ae7776a-3e61-42c6-9c86-5d278b28c597" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_b21d7f01-b0c6-4510-8846-e4d3d5d2acb0" xlink:to="loc_us-gaap_DebtInstrumentTable_0ae7776a-3e61-42c6-9c86-5d278b28c597" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_a8a94093-eb0a-43ea-89ee-731421e1ceb8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_0ae7776a-3e61-42c6-9c86-5d278b28c597" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_a8a94093-eb0a-43ea-89ee-731421e1ceb8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_a8a94093-eb0a-43ea-89ee-731421e1ceb8_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_a8a94093-eb0a-43ea-89ee-731421e1ceb8" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_a8a94093-eb0a-43ea-89ee-731421e1ceb8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_ff7e42dd-6f07-4939-a921-88f9e33ecbe7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_a8a94093-eb0a-43ea-89ee-731421e1ceb8" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_ff7e42dd-6f07-4939-a921-88f9e33ecbe7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesPayableToBanksMember_1cea748e-298e-4f2f-879a-3926cb314069" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NotesPayableToBanksMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_ff7e42dd-6f07-4939-a921-88f9e33ecbe7" xlink:to="loc_us-gaap_NotesPayableToBanksMember_1cea748e-298e-4f2f-879a-3926cb314069" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_5c892fe0-cbac-4d54-90ee-aab14b82d1ce" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_0ae7776a-3e61-42c6-9c86-5d278b28c597" xlink:to="loc_us-gaap_DebtInstrumentAxis_5c892fe0-cbac-4d54-90ee-aab14b82d1ce" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_5c892fe0-cbac-4d54-90ee-aab14b82d1ce_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_5c892fe0-cbac-4d54-90ee-aab14b82d1ce" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_5c892fe0-cbac-4d54-90ee-aab14b82d1ce_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_341deefe-817e-462c-9cab-aeec8dc38f04" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_5c892fe0-cbac-4d54-90ee-aab14b82d1ce" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_341deefe-817e-462c-9cab-aeec8dc38f04" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_LoanAndSecurityAgreementMember_88fd4fa6-5196-4318-99d8-f80f99c51b91" xlink:href="anab-20201231.xsd#anab_LoanAndSecurityAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_341deefe-817e-462c-9cab-aeec8dc38f04" xlink:to="loc_anab_LoanAndSecurityAgreementMember_88fd4fa6-5196-4318-99d8-f80f99c51b91" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_TermLoansMember_84454111-5486-4cb4-8251-cc7b1c3437c2" xlink:href="anab-20201231.xsd#anab_TermLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_anab_LoanAndSecurityAgreementMember_88fd4fa6-5196-4318-99d8-f80f99c51b91" xlink:to="loc_anab_TermLoansMember_84454111-5486-4cb4-8251-cc7b1c3437c2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_TermALoansMember_91427607-2a9c-4278-9a1a-46bdc84b9a1e" xlink:href="anab-20201231.xsd#anab_TermALoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_anab_TermLoansMember_84454111-5486-4cb4-8251-cc7b1c3437c2" xlink:to="loc_anab_TermALoansMember_91427607-2a9c-4278-9a1a-46bdc84b9a1e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_TermBLoansAndTermCLoansMember_d07ccda3-5d52-41c7-8d67-59f91ea5a71a" xlink:href="anab-20201231.xsd#anab_TermBLoansAndTermCLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_anab_TermLoansMember_84454111-5486-4cb4-8251-cc7b1c3437c2" xlink:to="loc_anab_TermBLoansAndTermCLoansMember_d07ccda3-5d52-41c7-8d67-59f91ea5a71a" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/FairValueMeasurementsandAvailableforSaleInvestments" xlink:type="simple" xlink:href="anab-20201231.xsd#FairValueMeasurementsandAvailableforSaleInvestments"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/FairValueMeasurementsandAvailableforSaleInvestments" xlink:type="extended" id="ibdd4fc90afa249b0bbec25efeaf1c6df_FairValueMeasurementsandAvailableforSaleInvestments"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/FairValueMeasurementsandAvailableforSaleInvestmentsTables" xlink:type="simple" xlink:href="anab-20201231.xsd#FairValueMeasurementsandAvailableforSaleInvestmentsTables"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/FairValueMeasurementsandAvailableforSaleInvestmentsTables" xlink:type="extended" id="i4c49179369424bdb80fa1c4ac86f7abf_FairValueMeasurementsandAvailableforSaleInvestmentsTables"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/FairValueMeasurementsandAvailableforSaleInvestmentsAssetsandLiabilitiesMeasuredatFairValueonaRecurringBasisDetails" xlink:type="simple" xlink:href="anab-20201231.xsd#FairValueMeasurementsandAvailableforSaleInvestmentsAssetsandLiabilitiesMeasuredatFairValueonaRecurringBasisDetails"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/FairValueMeasurementsandAvailableforSaleInvestmentsAssetsandLiabilitiesMeasuredatFairValueonaRecurringBasisDetails" xlink:type="extended" id="i824f3d6169914182859c59a15ab07f8e_FairValueMeasurementsandAvailableforSaleInvestmentsAssetsandLiabilitiesMeasuredatFairValueonaRecurringBasisDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_0a14448a-c649-4914-b292-6e900ddca91c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_CashAndCashEquivalentsAndRestrictedCashFairValueDisclosure_d6ad2ac7-07ce-42f0-8a76-c59f99d4e0e7" xlink:href="anab-20201231.xsd#anab_CashAndCashEquivalentsAndRestrictedCashFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_0a14448a-c649-4914-b292-6e900ddca91c" xlink:to="loc_anab_CashAndCashEquivalentsAndRestrictedCashFairValueDisclosure_d6ad2ac7-07ce-42f0-8a76-c59f99d4e0e7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_2966ad3a-3739-4d10-bd24-cb10ab9b0a4f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_0a14448a-c649-4914-b292-6e900ddca91c" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_2966ad3a-3739-4d10-bd24-cb10ab9b0a4f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_773b6c1d-6556-4193-bc31-52abd8993226" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_0a14448a-c649-4914-b292-6e900ddca91c" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_773b6c1d-6556-4193-bc31-52abd8993226" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_19f01a89-6f1c-412b-be79-6c7949c1fbec" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_773b6c1d-6556-4193-bc31-52abd8993226" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_19f01a89-6f1c-412b-be79-6c7949c1fbec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_19f01a89-6f1c-412b-be79-6c7949c1fbec_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_19f01a89-6f1c-412b-be79-6c7949c1fbec" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_19f01a89-6f1c-412b-be79-6c7949c1fbec_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_a10fe34c-7263-4535-a269-b3223d31edec" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_19f01a89-6f1c-412b-be79-6c7949c1fbec" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_a10fe34c-7263-4535-a269-b3223d31edec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_cd67f3cb-f6e6-44f3-8c97-585d2c0fa092" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementsRecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_a10fe34c-7263-4535-a269-b3223d31edec" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_cd67f3cb-f6e6-44f3-8c97-585d2c0fa092" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_e407ad4d-16ba-443a-a8aa-63028f487962" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_773b6c1d-6556-4193-bc31-52abd8993226" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_e407ad4d-16ba-443a-a8aa-63028f487962" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_e407ad4d-16ba-443a-a8aa-63028f487962_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_e407ad4d-16ba-443a-a8aa-63028f487962" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_e407ad4d-16ba-443a-a8aa-63028f487962_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_d2f27bd9-1e5e-41e2-bdc4-b2f56dbec1cf" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_e407ad4d-16ba-443a-a8aa-63028f487962" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_d2f27bd9-1e5e-41e2-bdc4-b2f56dbec1cf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_1b32e6e2-d17f-464d-ae7c-efb387d0ef3b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_d2f27bd9-1e5e-41e2-bdc4-b2f56dbec1cf" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_1b32e6e2-d17f-464d-ae7c-efb387d0ef3b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_a4e498f3-9582-4226-bc01-13bbca2a2ef4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_d2f27bd9-1e5e-41e2-bdc4-b2f56dbec1cf" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_a4e498f3-9582-4226-bc01-13bbca2a2ef4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_aa25ea47-1181-4895-a604-b55aa303f8cd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_d2f27bd9-1e5e-41e2-bdc4-b2f56dbec1cf" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_aa25ea47-1181-4895-a604-b55aa303f8cd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAxis_c99ebe54-0337-41ec-991f-5d81c13c5111" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashAndCashEquivalentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_773b6c1d-6556-4193-bc31-52abd8993226" xlink:to="loc_us-gaap_CashAndCashEquivalentsAxis_c99ebe54-0337-41ec-991f-5d81c13c5111" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_c99ebe54-0337-41ec-991f-5d81c13c5111_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_c99ebe54-0337-41ec-991f-5d81c13c5111" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_c99ebe54-0337-41ec-991f-5d81c13c5111_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_4b82db4c-e858-4ea8-afc8-03563531475f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_c99ebe54-0337-41ec-991f-5d81c13c5111" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_4b82db4c-e858-4ea8-afc8-03563531475f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MoneyMarketFundsMember_3cf85947-7a5e-4ec2-ab46-62b1ac29cdea" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_MoneyMarketFundsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_4b82db4c-e858-4ea8-afc8-03563531475f" xlink:to="loc_us-gaap_MoneyMarketFundsMember_3cf85947-7a5e-4ec2-ab46-62b1ac29cdea" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MutualFundMember_8529c00d-a905-4e00-bf2a-c522205fb58a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_MutualFundMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_4b82db4c-e858-4ea8-afc8-03563531475f" xlink:to="loc_us-gaap_MutualFundMember_8529c00d-a905-4e00-bf2a-c522205fb58a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_827e9a76-112b-49d2-90a0-d056fcb2e161" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_773b6c1d-6556-4193-bc31-52abd8993226" xlink:to="loc_us-gaap_FinancialInstrumentAxis_827e9a76-112b-49d2-90a0-d056fcb2e161" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_827e9a76-112b-49d2-90a0-d056fcb2e161_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_827e9a76-112b-49d2-90a0-d056fcb2e161" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_827e9a76-112b-49d2-90a0-d056fcb2e161_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_9788cf2b-c5fd-431e-8986-200d8fc4d831" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_827e9a76-112b-49d2-90a0-d056fcb2e161" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_9788cf2b-c5fd-431e-8986-200d8fc4d831" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_f69a96ac-bf89-4bf7-93cb-22214d697203" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_USTreasurySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_9788cf2b-c5fd-431e-8986-200d8fc4d831" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_f69a96ac-bf89-4bf7-93cb-22214d697203" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CertificatesOfDepositMember_e81f4ac1-ce3c-475a-a11d-4365fbcb9f22" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CertificatesOfDepositMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_9788cf2b-c5fd-431e-8986-200d8fc4d831" xlink:to="loc_us-gaap_CertificatesOfDepositMember_e81f4ac1-ce3c-475a-a11d-4365fbcb9f22" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_8c1b3135-73a4-4893-8576-3df50213adee" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_USGovernmentAgenciesDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_9788cf2b-c5fd-431e-8986-200d8fc4d831" xlink:to="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_8c1b3135-73a4-4893-8576-3df50213adee" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_CommercialAndCorporateObligationsMember_33043fc7-9831-4593-acb1-1086d6fe2cdd" xlink:href="anab-20201231.xsd#anab_CommercialAndCorporateObligationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_9788cf2b-c5fd-431e-8986-200d8fc4d831" xlink:to="loc_anab_CommercialAndCorporateObligationsMember_33043fc7-9831-4593-acb1-1086d6fe2cdd" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/FairValueMeasurementsandAvailableforSaleInvestmentsFairValueofOtherFinancialInstrumentsDetails" xlink:type="simple" xlink:href="anab-20201231.xsd#FairValueMeasurementsandAvailableforSaleInvestmentsFairValueofOtherFinancialInstrumentsDetails"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/FairValueMeasurementsandAvailableforSaleInvestmentsFairValueofOtherFinancialInstrumentsDetails" xlink:type="extended" id="i6b55db4766a141dfa42ba900d51d6e4b_FairValueMeasurementsandAvailableforSaleInvestmentsFairValueofOtherFinancialInstrumentsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_18b4cadf-289b-4165-ab0e-b5d5c0c534f3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesPayableFairValueDisclosure_7c40381b-fa9e-4af4-b3a0-f64aec686a6e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NotesPayableFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_18b4cadf-289b-4165-ab0e-b5d5c0c534f3" xlink:to="loc_us-gaap_NotesPayableFairValueDisclosure_7c40381b-fa9e-4af4-b3a0-f64aec686a6e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByBalanceSheetGroupingTable_9fdbdf71-07ba-48da-b77b-a35f7cb690c2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueByBalanceSheetGroupingTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_18b4cadf-289b-4165-ab0e-b5d5c0c534f3" xlink:to="loc_us-gaap_FairValueByBalanceSheetGroupingTable_9fdbdf71-07ba-48da-b77b-a35f7cb690c2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementBasisAxis_00b4ceef-2e8d-4993-957d-1f47fcc90281" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueByMeasurementBasisAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_9fdbdf71-07ba-48da-b77b-a35f7cb690c2" xlink:to="loc_us-gaap_FairValueByMeasurementBasisAxis_00b4ceef-2e8d-4993-957d-1f47fcc90281" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_00b4ceef-2e8d-4993-957d-1f47fcc90281_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_00b4ceef-2e8d-4993-957d-1f47fcc90281" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_00b4ceef-2e8d-4993-957d-1f47fcc90281_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueDisclosureItemAmountsDomain_1a03f2b2-9671-43d4-a6af-885a16a7ad53" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueDisclosureItemAmountsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_00b4ceef-2e8d-4993-957d-1f47fcc90281" xlink:to="loc_us-gaap_FairValueDisclosureItemAmountsDomain_1a03f2b2-9671-43d4-a6af-885a16a7ad53" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_bfeb6133-eaf7-4d26-8f53-644227fea845" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_1a03f2b2-9671-43d4-a6af-885a16a7ad53" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_bfeb6133-eaf7-4d26-8f53-644227fea845" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_a52e7c23-2ab5-4ff4-863e-f3c461e2e643" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CarryingReportedAmountFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_1a03f2b2-9671-43d4-a6af-885a16a7ad53" xlink:to="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_a52e7c23-2ab5-4ff4-863e-f3c461e2e643" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_4f0e1f4a-8572-43c3-bcb9-0d8a5bc4952c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EstimateOfFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_1a03f2b2-9671-43d4-a6af-885a16a7ad53" xlink:to="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_4f0e1f4a-8572-43c3-bcb9-0d8a5bc4952c" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/FairValueMeasurementsandAvailableforSaleInvestmentsAvailableforsaleInvestmentsDetails" xlink:type="simple" xlink:href="anab-20201231.xsd#FairValueMeasurementsandAvailableforSaleInvestmentsAvailableforsaleInvestmentsDetails"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/FairValueMeasurementsandAvailableforSaleInvestmentsAvailableforsaleInvestmentsDetails" xlink:type="extended" id="i3d12c49e9758435e82232ff6245985ac_FairValueMeasurementsandAvailableforSaleInvestmentsAvailableforsaleInvestmentsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_182ae82e-c8dd-48d7-9084-6554cd8a03c9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_ce87987f-5d57-4f8f-bf09-6e76ce87eb78" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_182ae82e-c8dd-48d7-9084-6554cd8a03c9" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_ce87987f-5d57-4f8f-bf09-6e76ce87eb78" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_43d1c146-ad6b-471f-8c2b-73b6db5e8076" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_182ae82e-c8dd-48d7-9084-6554cd8a03c9" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_43d1c146-ad6b-471f-8c2b-73b6db5e8076" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_7efc619e-cbbf-495f-9237-d6b46fa131f2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_182ae82e-c8dd-48d7-9084-6554cd8a03c9" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_7efc619e-cbbf-495f-9237-d6b46fa131f2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_6960bf22-7744-4b8d-902b-279cb373f134" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_182ae82e-c8dd-48d7-9084-6554cd8a03c9" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_6960bf22-7744-4b8d-902b-279cb373f134" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent_e146d412-b2a6-4b9e-b381-c001a93273eb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_182ae82e-c8dd-48d7-9084-6554cd8a03c9" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent_e146d412-b2a6-4b9e-b381-c001a93273eb" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent_a7d85669-174b-467c-a8ed-6157fbfb4c4e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_182ae82e-c8dd-48d7-9084-6554cd8a03c9" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent_a7d85669-174b-467c-a8ed-6157fbfb4c4e" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_AvailableforsaleDebtSecuritiesRemainingMaturity_9bcff51a-2bbd-493d-bad0-6b21bd3f3000" xlink:href="anab-20201231.xsd#anab_AvailableforsaleDebtSecuritiesRemainingMaturity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_182ae82e-c8dd-48d7-9084-6554cd8a03c9" xlink:to="loc_anab_AvailableforsaleDebtSecuritiesRemainingMaturity_9bcff51a-2bbd-493d-bad0-6b21bd3f3000" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_1451f289-1aac-40ae-a4c0-83cad8738f88" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtSecuritiesAvailableForSaleTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_182ae82e-c8dd-48d7-9084-6554cd8a03c9" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_1451f289-1aac-40ae-a4c0-83cad8738f88" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_25e629b0-2896-425b-ab96-b500f74851be" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_1451f289-1aac-40ae-a4c0-83cad8738f88" xlink:to="loc_us-gaap_FinancialInstrumentAxis_25e629b0-2896-425b-ab96-b500f74851be" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_25e629b0-2896-425b-ab96-b500f74851be_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_25e629b0-2896-425b-ab96-b500f74851be" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_25e629b0-2896-425b-ab96-b500f74851be_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_ba47c6d0-5b94-40ae-b27a-e3ffeb0ec89f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_25e629b0-2896-425b-ab96-b500f74851be" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_ba47c6d0-5b94-40ae-b27a-e3ffeb0ec89f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_d351d997-958f-4768-9960-e39e2ed00696" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_USGovernmentAgenciesDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_ba47c6d0-5b94-40ae-b27a-e3ffeb0ec89f" xlink:to="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_d351d997-958f-4768-9960-e39e2ed00696" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CertificatesOfDepositMember_fcb6edca-4fbd-470d-a1a8-a57ee7b3731e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CertificatesOfDepositMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_ba47c6d0-5b94-40ae-b27a-e3ffeb0ec89f" xlink:to="loc_us-gaap_CertificatesOfDepositMember_fcb6edca-4fbd-470d-a1a8-a57ee7b3731e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_CommercialAndCorporateObligationsMember_ee4e2ff2-64c2-45ef-ba7b-3ee5919e6db7" xlink:href="anab-20201231.xsd#anab_CommercialAndCorporateObligationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_ba47c6d0-5b94-40ae-b27a-e3ffeb0ec89f" xlink:to="loc_anab_CommercialAndCorporateObligationsMember_ee4e2ff2-64c2-45ef-ba7b-3ee5919e6db7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_861b02f6-dd43-4f17-b826-0eee1f7f5679" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_USTreasurySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_ba47c6d0-5b94-40ae-b27a-e3ffeb0ec89f" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_861b02f6-dd43-4f17-b826-0eee1f7f5679" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_b2de9d7c-1cbe-4cf8-84d3-e59d3e2511a1" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_1451f289-1aac-40ae-a4c0-83cad8738f88" xlink:to="loc_srt_RangeAxis_b2de9d7c-1cbe-4cf8-84d3-e59d3e2511a1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_b2de9d7c-1cbe-4cf8-84d3-e59d3e2511a1_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_b2de9d7c-1cbe-4cf8-84d3-e59d3e2511a1" xlink:to="loc_srt_RangeMember_b2de9d7c-1cbe-4cf8-84d3-e59d3e2511a1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_a39bdd7c-ab91-4795-9187-3fb2ff267e6a" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_b2de9d7c-1cbe-4cf8-84d3-e59d3e2511a1" xlink:to="loc_srt_RangeMember_a39bdd7c-ab91-4795-9187-3fb2ff267e6a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_86b2d002-f2d4-4254-b9a3-4d35e0439d39" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_a39bdd7c-ab91-4795-9187-3fb2ff267e6a" xlink:to="loc_srt_MinimumMember_86b2d002-f2d4-4254-b9a3-4d35e0439d39" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_1594fca3-ecd2-4715-9824-9644c3fd2ea1" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_a39bdd7c-ab91-4795-9187-3fb2ff267e6a" xlink:to="loc_srt_MaximumMember_1594fca3-ecd2-4715-9824-9644c3fd2ea1" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/FairValueMeasurementsandAvailableforSaleInvestmentsScheduleofUnrealizedLossandFairValuesinaLossPositionDetails" xlink:type="simple" xlink:href="anab-20201231.xsd#FairValueMeasurementsandAvailableforSaleInvestmentsScheduleofUnrealizedLossandFairValuesinaLossPositionDetails"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/FairValueMeasurementsandAvailableforSaleInvestmentsScheduleofUnrealizedLossandFairValuesinaLossPositionDetails" xlink:type="extended" id="i9559261bd54d4611bcd195c58cdc6c89_FairValueMeasurementsandAvailableforSaleInvestmentsScheduleofUnrealizedLossandFairValuesinaLossPositionDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_5c191399-0360-4bca-a746-dba936392ffe" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months_28265818-30fc-4398-8028-1ee83e8e6638" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_5c191399-0360-4bca-a746-dba936392ffe" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months_28265818-30fc-4398-8028-1ee83e8e6638" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss_4e926967-b5ec-4743-889d-e5c8f713d536" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_5c191399-0360-4bca-a746-dba936392ffe" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss_4e926967-b5ec-4743-889d-e5c8f713d536" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger_249f596c-108e-4565-945f-8a45fc4d44c4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_5c191399-0360-4bca-a746-dba936392ffe" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger_249f596c-108e-4565-945f-8a45fc4d44c4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss_18624a45-f0a2-4719-b81e-361f1b1bd40b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_5c191399-0360-4bca-a746-dba936392ffe" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss_18624a45-f0a2-4719-b81e-361f1b1bd40b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition_1b2c6ffa-215b-4196-8c1e-f459e572087c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_5c191399-0360-4bca-a746-dba936392ffe" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition_1b2c6ffa-215b-4196-8c1e-f459e572087c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss_25c15999-35b6-4ed5-a5d7-c2f6ea1b93ce" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_5c191399-0360-4bca-a746-dba936392ffe" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss_25c15999-35b6-4ed5-a5d7-c2f6ea1b93ce" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_bafc68ad-3781-4cc9-b71c-c0be431a8695" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtSecuritiesAvailableForSaleTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_5c191399-0360-4bca-a746-dba936392ffe" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_bafc68ad-3781-4cc9-b71c-c0be431a8695" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_e7b6e4d7-b722-4f7c-9cbb-e685fc20758f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_bafc68ad-3781-4cc9-b71c-c0be431a8695" xlink:to="loc_us-gaap_FinancialInstrumentAxis_e7b6e4d7-b722-4f7c-9cbb-e685fc20758f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_e7b6e4d7-b722-4f7c-9cbb-e685fc20758f_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_e7b6e4d7-b722-4f7c-9cbb-e685fc20758f" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_e7b6e4d7-b722-4f7c-9cbb-e685fc20758f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_5ba0b262-05e2-46aa-b8fe-1b60d5659375" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_e7b6e4d7-b722-4f7c-9cbb-e685fc20758f" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_5ba0b262-05e2-46aa-b8fe-1b60d5659375" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_53fcf367-b53b-477c-a75b-e0d9c0fca78a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_USGovernmentAgenciesDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_5ba0b262-05e2-46aa-b8fe-1b60d5659375" xlink:to="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_53fcf367-b53b-477c-a75b-e0d9c0fca78a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_CommercialAndCorporateObligationsMember_1523c1a3-28c0-469a-8c79-b4dde962d2f4" xlink:href="anab-20201231.xsd#anab_CommercialAndCorporateObligationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_5ba0b262-05e2-46aa-b8fe-1b60d5659375" xlink:to="loc_anab_CommercialAndCorporateObligationsMember_1523c1a3-28c0-469a-8c79-b4dde962d2f4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_bcbd902c-81a7-4175-bb70-508365117a6d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_USTreasurySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_5ba0b262-05e2-46aa-b8fe-1b60d5659375" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_bcbd902c-81a7-4175-bb70-508365117a6d" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/FairValueMeasurementsandAvailableforSaleInvestmentsNarrativeDetails" xlink:type="simple" xlink:href="anab-20201231.xsd#FairValueMeasurementsandAvailableforSaleInvestmentsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/FairValueMeasurementsandAvailableforSaleInvestmentsNarrativeDetails" xlink:type="extended" id="i05d76b8f2143429fa9baf4590e7f60d6_FairValueMeasurementsandAvailableforSaleInvestmentsNarrativeDetails"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/StockholdersEquity" xlink:type="simple" xlink:href="anab-20201231.xsd#StockholdersEquity"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/StockholdersEquity" xlink:type="extended" id="i9948354affb74e5a8b2a8f403221ce9b_StockholdersEquity"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/StockholdersEquityTables" xlink:type="simple" xlink:href="anab-20201231.xsd#StockholdersEquityTables"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/StockholdersEquityTables" xlink:type="extended" id="i3f5fe8d543a74cfcb5ac17eeb4353eae_StockholdersEquityTables"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/StockholdersEquityAdditionalInformationDetails" xlink:type="simple" xlink:href="anab-20201231.xsd#StockholdersEquityAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/StockholdersEquityAdditionalInformationDetails" xlink:type="extended" id="i4e4affab9a564b8abdc5712a00996672_StockholdersEquityAdditionalInformationDetails"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/StockholdersEquitySummaryofCommonStockReservedforFutureIssuanceDetails" xlink:type="simple" xlink:href="anab-20201231.xsd#StockholdersEquitySummaryofCommonStockReservedforFutureIssuanceDetails"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/StockholdersEquitySummaryofCommonStockReservedforFutureIssuanceDetails" xlink:type="extended" id="ide092856255f4fc9a6b27d2c1d8449be_StockholdersEquitySummaryofCommonStockReservedforFutureIssuanceDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockLineItems_ab66173c-5ef2-4913-8495-1bb001d60cdd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ClassOfStockLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockNumberOfSharesParValueAndOtherDisclosuresAbstract_3ced8fcc-553a-422b-9be5-a23b422bfe65" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockNumberOfSharesParValueAndOtherDisclosuresAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_ab66173c-5ef2-4913-8495-1bb001d60cdd" xlink:to="loc_us-gaap_CommonStockNumberOfSharesParValueAndOtherDisclosuresAbstract_3ced8fcc-553a-422b-9be5-a23b422bfe65" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_f81fc0c8-2869-43f3-bd42-30d539eaa13e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CommonStockNumberOfSharesParValueAndOtherDisclosuresAbstract_3ced8fcc-553a-422b-9be5-a23b422bfe65" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_f81fc0c8-2869-43f3-bd42-30d539eaa13e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_b1c1fc0a-1a5f-4249-b535-18e848efd931" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_ab66173c-5ef2-4913-8495-1bb001d60cdd" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_b1c1fc0a-1a5f-4249-b535-18e848efd931" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_7ef07844-1fdc-4ef8-aafd-d36ec02e3c61" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockCapitalSharesReservedForFutureIssuance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_ab66173c-5ef2-4913-8495-1bb001d60cdd" xlink:to="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_7ef07844-1fdc-4ef8-aafd-d36ec02e3c61" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_c52e376b-886c-40a2-bab0-77516c186d7e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfStockByClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_ab66173c-5ef2-4913-8495-1bb001d60cdd" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_c52e376b-886c-40a2-bab0-77516c186d7e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_137c114b-7b63-43e3-9674-eea6cf1f24bf" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_c52e376b-886c-40a2-bab0-77516c186d7e" xlink:to="loc_us-gaap_PlanNameAxis_137c114b-7b63-43e3-9674-eea6cf1f24bf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_137c114b-7b63-43e3-9674-eea6cf1f24bf_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_137c114b-7b63-43e3-9674-eea6cf1f24bf" xlink:to="loc_us-gaap_PlanNameDomain_137c114b-7b63-43e3-9674-eea6cf1f24bf_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_c9330fc1-f02f-4458-b2e4-6d3ac5dc34cb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_137c114b-7b63-43e3-9674-eea6cf1f24bf" xlink:to="loc_us-gaap_PlanNameDomain_c9330fc1-f02f-4458-b2e4-6d3ac5dc34cb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_EquityIncentivePlan2017Member_9388b698-1d18-4efc-9e4a-2792fc715aef" xlink:href="anab-20201231.xsd#anab_EquityIncentivePlan2017Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_c9330fc1-f02f-4458-b2e4-6d3ac5dc34cb" xlink:to="loc_anab_EquityIncentivePlan2017Member_9388b698-1d18-4efc-9e4a-2792fc715aef" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_EmployeeStockPurchasePlan2017Member_8a6f27d9-ca18-45f1-81f8-6b3a3e43ec95" xlink:href="anab-20201231.xsd#anab_EmployeeStockPurchasePlan2017Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_c9330fc1-f02f-4458-b2e4-6d3ac5dc34cb" xlink:to="loc_anab_EmployeeStockPurchasePlan2017Member_8a6f27d9-ca18-45f1-81f8-6b3a3e43ec95" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/EquityIncentivePlans" xlink:type="simple" xlink:href="anab-20201231.xsd#EquityIncentivePlans"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/EquityIncentivePlans" xlink:type="extended" id="i6b804d73414941318b3cfcd8f3fbfdac_EquityIncentivePlans"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/EquityIncentivePlansTables" xlink:type="simple" xlink:href="anab-20201231.xsd#EquityIncentivePlansTables"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/EquityIncentivePlansTables" xlink:type="extended" id="ib87533ea0d254bb1965cd0526efea360_EquityIncentivePlansTables"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/EquityIncentivePlansNarrativeDetails" xlink:type="simple" xlink:href="anab-20201231.xsd#EquityIncentivePlansNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/EquityIncentivePlansNarrativeDetails" xlink:type="extended" id="id335f8902c144fd08dcdf649cdea8dfb_EquityIncentivePlansNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_641f7701-75d3-4d4e-9477-dca8b5fac30c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_CommonStockCapitalSharesReservedForFutureIssuanceAnnualIncreasePercentOfAggregateSharesOutstanding_10e73a96-8a7f-478f-ba7c-93c9e886904b" xlink:href="anab-20201231.xsd#anab_CommonStockCapitalSharesReservedForFutureIssuanceAnnualIncreasePercentOfAggregateSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_641f7701-75d3-4d4e-9477-dca8b5fac30c" xlink:to="loc_anab_CommonStockCapitalSharesReservedForFutureIssuanceAnnualIncreasePercentOfAggregateSharesOutstanding_10e73a96-8a7f-478f-ba7c-93c9e886904b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_CommonStockCapitalSharesReservedForFutureIssuanceIncrease_3b9388ed-38d4-4298-834f-e77009e23398" xlink:href="anab-20201231.xsd#anab_CommonStockCapitalSharesReservedForFutureIssuanceIncrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_641f7701-75d3-4d4e-9477-dca8b5fac30c" xlink:to="loc_anab_CommonStockCapitalSharesReservedForFutureIssuanceIncrease_3b9388ed-38d4-4298-834f-e77009e23398" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_15ac1dc4-1dc1-4ac9-b0de-3481ce952f5b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_641f7701-75d3-4d4e-9477-dca8b5fac30c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_15ac1dc4-1dc1-4ac9-b0de-3481ce952f5b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_13260158-e510-450f-b787-6edf83f0015f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_641f7701-75d3-4d4e-9477-dca8b5fac30c" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_13260158-e510-450f-b787-6edf83f0015f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromStockOptionsExercised_d3a7fb0f-29e6-4f33-9817-21a59a8d8bde" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_641f7701-75d3-4d4e-9477-dca8b5fac30c" xlink:to="loc_us-gaap_ProceedsFromStockOptionsExercised_d3a7fb0f-29e6-4f33-9817-21a59a8d8bde" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_EmployeeAndNonemployeeServiceSharebasedCompensationNonvestedAwardsCompensationNotYetRecognizedStockOptions_743c13b8-d91f-427d-8f97-e4fb45e4d48c" xlink:href="anab-20201231.xsd#anab_EmployeeAndNonemployeeServiceSharebasedCompensationNonvestedAwardsCompensationNotYetRecognizedStockOptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_641f7701-75d3-4d4e-9477-dca8b5fac30c" xlink:to="loc_anab_EmployeeAndNonemployeeServiceSharebasedCompensationNonvestedAwardsCompensationNotYetRecognizedStockOptions_743c13b8-d91f-427d-8f97-e4fb45e4d48c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_EmployeeAndNonemployeeServiceSharebasedCompensationNonvestedAwardsCompensationCostNotYetRecognizedPeriodForRecognition_435dab06-f057-4c2c-8277-af2ee3b97d61" xlink:href="anab-20201231.xsd#anab_EmployeeAndNonemployeeServiceSharebasedCompensationNonvestedAwardsCompensationCostNotYetRecognizedPeriodForRecognition"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_641f7701-75d3-4d4e-9477-dca8b5fac30c" xlink:to="loc_anab_EmployeeAndNonemployeeServiceSharebasedCompensationNonvestedAwardsCompensationCostNotYetRecognizedPeriodForRecognition_435dab06-f057-4c2c-8277-af2ee3b97d61" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_35e20405-3c0d-4e44-8cc2-9ac4c9d56853" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_641f7701-75d3-4d4e-9477-dca8b5fac30c" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_35e20405-3c0d-4e44-8cc2-9ac4c9d56853" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_4716f5a4-81f7-4eab-9e4c-57b84038d62c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_35e20405-3c0d-4e44-8cc2-9ac4c9d56853" xlink:to="loc_us-gaap_PlanNameAxis_4716f5a4-81f7-4eab-9e4c-57b84038d62c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_4716f5a4-81f7-4eab-9e4c-57b84038d62c_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_4716f5a4-81f7-4eab-9e4c-57b84038d62c" xlink:to="loc_us-gaap_PlanNameDomain_4716f5a4-81f7-4eab-9e4c-57b84038d62c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_9deeff36-8104-45e9-a8c1-4f67a5ef094a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_4716f5a4-81f7-4eab-9e4c-57b84038d62c" xlink:to="loc_us-gaap_PlanNameDomain_9deeff36-8104-45e9-a8c1-4f67a5ef094a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_EquityIncentivePlan2017Member_f1ab41de-5003-4b5d-8de6-21aec7c0737b" xlink:href="anab-20201231.xsd#anab_EquityIncentivePlan2017Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_9deeff36-8104-45e9-a8c1-4f67a5ef094a" xlink:to="loc_anab_EquityIncentivePlan2017Member_f1ab41de-5003-4b5d-8de6-21aec7c0737b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_EmployeeStockPurchasePlan2017Member_e660f13a-6654-4d02-a704-51a3b50d70e6" xlink:href="anab-20201231.xsd#anab_EmployeeStockPurchasePlan2017Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_9deeff36-8104-45e9-a8c1-4f67a5ef094a" xlink:to="loc_anab_EmployeeStockPurchasePlan2017Member_e660f13a-6654-4d02-a704-51a3b50d70e6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_acad4f39-74be-4baa-a004-61d18cb0243d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_35e20405-3c0d-4e44-8cc2-9ac4c9d56853" xlink:to="loc_us-gaap_AwardTypeAxis_acad4f39-74be-4baa-a004-61d18cb0243d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_acad4f39-74be-4baa-a004-61d18cb0243d_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_acad4f39-74be-4baa-a004-61d18cb0243d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_acad4f39-74be-4baa-a004-61d18cb0243d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_ca619671-7998-4ba1-b4e1-a3c7f938f588" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_acad4f39-74be-4baa-a004-61d18cb0243d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_ca619671-7998-4ba1-b4e1-a3c7f938f588" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockMember_34d0d519-69ea-4c54-9d29-545be5af3f23" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EmployeeStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_ca619671-7998-4ba1-b4e1-a3c7f938f588" xlink:to="loc_us-gaap_EmployeeStockMember_34d0d519-69ea-4c54-9d29-545be5af3f23" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_EmployeeAndNonemployeeStockOptionsMember_c978159f-13f4-4981-be7f-f32aaae5b168" xlink:href="anab-20201231.xsd#anab_EmployeeAndNonemployeeStockOptionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_ca619671-7998-4ba1-b4e1-a3c7f938f588" xlink:to="loc_anab_EmployeeAndNonemployeeStockOptionsMember_c978159f-13f4-4981-be7f-f32aaae5b168" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_43c51171-669f-43ea-af67-2886066703d9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_ca619671-7998-4ba1-b4e1-a3c7f938f588" xlink:to="loc_us-gaap_EmployeeStockOptionMember_43c51171-669f-43ea-af67-2886066703d9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_TitleOfIndividualAxis_752600f3-2d96-4f7c-80a2-107ad4116a3e" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_TitleOfIndividualAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_35e20405-3c0d-4e44-8cc2-9ac4c9d56853" xlink:to="loc_srt_TitleOfIndividualAxis_752600f3-2d96-4f7c-80a2-107ad4116a3e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_752600f3-2d96-4f7c-80a2-107ad4116a3e_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_TitleOfIndividualWithRelationshipToEntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_TitleOfIndividualAxis_752600f3-2d96-4f7c-80a2-107ad4116a3e" xlink:to="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_752600f3-2d96-4f7c-80a2-107ad4116a3e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_a129654a-b8fa-4c2e-b32a-726831c79a62" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_TitleOfIndividualWithRelationshipToEntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_TitleOfIndividualAxis_752600f3-2d96-4f7c-80a2-107ad4116a3e" xlink:to="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_a129654a-b8fa-4c2e-b32a-726831c79a62" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_DirectorMember_32803a5f-1b3f-4e0c-9d09-ae3c94b68902" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_DirectorMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_a129654a-b8fa-4c2e-b32a-726831c79a62" xlink:to="loc_srt_DirectorMember_32803a5f-1b3f-4e0c-9d09-ae3c94b68902" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/EquityIncentivePlansOptionActivityDetails" xlink:type="simple" xlink:href="anab-20201231.xsd#EquityIncentivePlansOptionActivityDetails"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/EquityIncentivePlansOptionActivityDetails" xlink:type="extended" id="i22f78d2acce044848fdf19ad47377439_EquityIncentivePlansOptionActivityDetails"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/EquityIncentivePlansOptionFairValueAssumptionsDetails" xlink:type="simple" xlink:href="anab-20201231.xsd#EquityIncentivePlansOptionFairValueAssumptionsDetails"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/EquityIncentivePlansOptionFairValueAssumptionsDetails" xlink:type="extended" id="i219fa131a1b04a339fb6d02d41c0c985_EquityIncentivePlansOptionFairValueAssumptionsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_82a934f1-a3d3-4d22-8fe4-76b2333f4926" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_c556a8a4-ec9b-4542-b54d-bba3a3210f6f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_82a934f1-a3d3-4d22-8fe4-76b2333f4926" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_c556a8a4-ec9b-4542-b54d-bba3a3210f6f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_84dced02-ebc9-4ed6-9cc4-1b9cf9c2f336" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_82a934f1-a3d3-4d22-8fe4-76b2333f4926" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_84dced02-ebc9-4ed6-9cc4-1b9cf9c2f336" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_2899bba0-63f5-4413-ac2e-800b2b650ca4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_82a934f1-a3d3-4d22-8fe4-76b2333f4926" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_2899bba0-63f5-4413-ac2e-800b2b650ca4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_bf519760-0d77-40e7-903a-1f49999eb8da" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_82a934f1-a3d3-4d22-8fe4-76b2333f4926" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_bf519760-0d77-40e7-903a-1f49999eb8da" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_f1f14849-346d-4017-b84b-c2e1aeb2cfd0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_82a934f1-a3d3-4d22-8fe4-76b2333f4926" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_f1f14849-346d-4017-b84b-c2e1aeb2cfd0" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_81aea42b-12b1-46ef-8701-a4241f16f09b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_82a934f1-a3d3-4d22-8fe4-76b2333f4926" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_81aea42b-12b1-46ef-8701-a4241f16f09b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_328c47c8-f77f-420d-a754-e3e59a1527cd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_81aea42b-12b1-46ef-8701-a4241f16f09b" xlink:to="loc_us-gaap_AwardTypeAxis_328c47c8-f77f-420d-a754-e3e59a1527cd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_328c47c8-f77f-420d-a754-e3e59a1527cd_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_328c47c8-f77f-420d-a754-e3e59a1527cd" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_328c47c8-f77f-420d-a754-e3e59a1527cd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_eb5e8e06-9391-4e3c-b2e9-bad039b9120b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_328c47c8-f77f-420d-a754-e3e59a1527cd" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_eb5e8e06-9391-4e3c-b2e9-bad039b9120b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_6bafd46d-dda7-4427-b7ad-fd16569f0297" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_eb5e8e06-9391-4e3c-b2e9-bad039b9120b" xlink:to="loc_us-gaap_EmployeeStockOptionMember_6bafd46d-dda7-4427-b7ad-fd16569f0297" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/EquityIncentivePlansAllocationofSharebasedCompensationExpenseDetails" xlink:type="simple" xlink:href="anab-20201231.xsd#EquityIncentivePlansAllocationofSharebasedCompensationExpenseDetails"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/EquityIncentivePlansAllocationofSharebasedCompensationExpenseDetails" xlink:type="extended" id="ic0ccfa3be67a459c9efa9f6e64cb973c_EquityIncentivePlansAllocationofSharebasedCompensationExpenseDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_2f38f55d-7d23-4e88-8e9c-f4a474a4670f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_SharebasedCompensationAndIssuanceOfStockAndWarrantsForServicesOrClaims_18f81ae7-969b-411a-8c4b-e4820496975b" xlink:href="anab-20201231.xsd#anab_SharebasedCompensationAndIssuanceOfStockAndWarrantsForServicesOrClaims"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_2f38f55d-7d23-4e88-8e9c-f4a474a4670f" xlink:to="loc_anab_SharebasedCompensationAndIssuanceOfStockAndWarrantsForServicesOrClaims_18f81ae7-969b-411a-8c4b-e4820496975b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_dec3ace5-533e-4a94-898c-8de2a5ed37d3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_2f38f55d-7d23-4e88-8e9c-f4a474a4670f" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_dec3ace5-533e-4a94-898c-8de2a5ed37d3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_39d5a26c-6e8a-43ed-857c-e354ed9f6228" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_dec3ace5-533e-4a94-898c-8de2a5ed37d3" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_39d5a26c-6e8a-43ed-857c-e354ed9f6228" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_39d5a26c-6e8a-43ed-857c-e354ed9f6228_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_39d5a26c-6e8a-43ed-857c-e354ed9f6228" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_39d5a26c-6e8a-43ed-857c-e354ed9f6228_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_b6131ea7-3ad3-4aa7-9f57-c926f1393393" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_39d5a26c-6e8a-43ed-857c-e354ed9f6228" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_b6131ea7-3ad3-4aa7-9f57-c926f1393393" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpenseMember_4f86c406-190a-45b9-8e72-aff8d513eaca" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ResearchAndDevelopmentExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_b6131ea7-3ad3-4aa7-9f57-c926f1393393" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpenseMember_4f86c406-190a-45b9-8e72-aff8d513eaca" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpenseMember_b2168f5a-bb15-4634-8b29-913b884d8ebe" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GeneralAndAdministrativeExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_b6131ea7-3ad3-4aa7-9f57-c926f1393393" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpenseMember_b2168f5a-bb15-4634-8b29-913b884d8ebe" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/AustraliaResearchandDevelopmentTaxIncentive" xlink:type="simple" xlink:href="anab-20201231.xsd#AustraliaResearchandDevelopmentTaxIncentive"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/AustraliaResearchandDevelopmentTaxIncentive" xlink:type="extended" id="if7f74055691c4d9fbaa8e0e3ae954686_AustraliaResearchandDevelopmentTaxIncentive"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/AustraliaResearchandDevelopmentTaxIncentiveDetails" xlink:type="simple" xlink:href="anab-20201231.xsd#AustraliaResearchandDevelopmentTaxIncentiveDetails"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/AustraliaResearchandDevelopmentTaxIncentiveDetails" xlink:type="extended" id="i679c3c2a99ae4f9e8bf6882c813f1e00_AustraliaResearchandDevelopmentTaxIncentiveDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxCreditCarryforwardLineItems_9276c7da-44f0-42e1-a00c-c0b1f3d01294" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TaxCreditCarryforwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_ResearchAndDevelopmentTaxIncentiveCreditPercentage_667f3103-6fe1-4482-b739-321d55fa777e" xlink:href="anab-20201231.xsd#anab_ResearchAndDevelopmentTaxIncentiveCreditPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TaxCreditCarryforwardLineItems_9276c7da-44f0-42e1-a00c-c0b1f3d01294" xlink:to="loc_anab_ResearchAndDevelopmentTaxIncentiveCreditPercentage_667f3103-6fe1-4482-b739-321d55fa777e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_ResearchAndDevelopmentTaxIncentiveCredit_5e538510-6d2a-407a-98a1-357b33817c91" xlink:href="anab-20201231.xsd#anab_ResearchAndDevelopmentTaxIncentiveCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TaxCreditCarryforwardLineItems_9276c7da-44f0-42e1-a00c-c0b1f3d01294" xlink:to="loc_anab_ResearchAndDevelopmentTaxIncentiveCredit_5e538510-6d2a-407a-98a1-357b33817c91" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_ResearchAndDevelopmentTaxIncentiveCreditReceivedDuringPeriod_48ae0ba3-cdbf-4934-a900-fbda75e0748b" xlink:href="anab-20201231.xsd#anab_ResearchAndDevelopmentTaxIncentiveCreditReceivedDuringPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TaxCreditCarryforwardLineItems_9276c7da-44f0-42e1-a00c-c0b1f3d01294" xlink:to="loc_anab_ResearchAndDevelopmentTaxIncentiveCreditReceivedDuringPeriod_48ae0ba3-cdbf-4934-a900-fbda75e0748b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_ResearchAndDevelopmentTaxIncentiveCreditReceivableCurrent_bdef2c39-7550-4f74-a997-2da4779a4c6a" xlink:href="anab-20201231.xsd#anab_ResearchAndDevelopmentTaxIncentiveCreditReceivableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TaxCreditCarryforwardLineItems_9276c7da-44f0-42e1-a00c-c0b1f3d01294" xlink:to="loc_anab_ResearchAndDevelopmentTaxIncentiveCreditReceivableCurrent_bdef2c39-7550-4f74-a997-2da4779a4c6a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxCreditCarryforwardTable_dc3edc78-7ce8-4a12-8f31-28f380510b08" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TaxCreditCarryforwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_TaxCreditCarryforwardLineItems_9276c7da-44f0-42e1-a00c-c0b1f3d01294" xlink:to="loc_us-gaap_TaxCreditCarryforwardTable_dc3edc78-7ce8-4a12-8f31-28f380510b08" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityNameAxis_433e1913-4c67-41d8-a902-28f52b54315f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxAuthorityNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_TaxCreditCarryforwardTable_dc3edc78-7ce8-4a12-8f31-28f380510b08" xlink:to="loc_us-gaap_IncomeTaxAuthorityNameAxis_433e1913-4c67-41d8-a902-28f52b54315f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityNameDomain_433e1913-4c67-41d8-a902-28f52b54315f_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxAuthorityNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeTaxAuthorityNameAxis_433e1913-4c67-41d8-a902-28f52b54315f" xlink:to="loc_us-gaap_IncomeTaxAuthorityNameDomain_433e1913-4c67-41d8-a902-28f52b54315f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityNameDomain_e9174a78-70d4-4cf8-8fbf-eedf39e76850" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxAuthorityNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeTaxAuthorityNameAxis_433e1913-4c67-41d8-a902-28f52b54315f" xlink:to="loc_us-gaap_IncomeTaxAuthorityNameDomain_e9174a78-70d4-4cf8-8fbf-eedf39e76850" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AustralianTaxationOfficeMember_0a972c10-b17c-4344-9ccd-82088c0e5d50" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AustralianTaxationOfficeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityNameDomain_e9174a78-70d4-4cf8-8fbf-eedf39e76850" xlink:to="loc_us-gaap_AustralianTaxationOfficeMember_0a972c10-b17c-4344-9ccd-82088c0e5d50" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_2f826d6a-bf26-4fe7-a4af-708f913a3295" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_TaxCreditCarryforwardTable_dc3edc78-7ce8-4a12-8f31-28f380510b08" xlink:to="loc_srt_ConsolidatedEntitiesAxis_2f826d6a-bf26-4fe7-a4af-708f913a3295" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_2f826d6a-bf26-4fe7-a4af-708f913a3295_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_2f826d6a-bf26-4fe7-a4af-708f913a3295" xlink:to="loc_srt_ConsolidatedEntitiesDomain_2f826d6a-bf26-4fe7-a4af-708f913a3295_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_e5040bef-aae4-488b-b349-b05574debca8" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_2f826d6a-bf26-4fe7-a4af-708f913a3295" xlink:to="loc_srt_ConsolidatedEntitiesDomain_e5040bef-aae4-488b-b349-b05574debca8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SubsidiariesMember_e2886272-cf35-48b1-8dc4-bf8ab33ca5a9" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_SubsidiariesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_e5040bef-aae4-488b-b349-b05574debca8" xlink:to="loc_srt_SubsidiariesMember_e2886272-cf35-48b1-8dc4-bf8ab33ca5a9" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/EmployeeBenefitPlan" xlink:type="simple" xlink:href="anab-20201231.xsd#EmployeeBenefitPlan"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/EmployeeBenefitPlan" xlink:type="extended" id="i040331fc9b13432db14a73bb81c32e33_EmployeeBenefitPlan"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/EmployeeBenefitPlanDetails" xlink:type="simple" xlink:href="anab-20201231.xsd#EmployeeBenefitPlanDetails"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/EmployeeBenefitPlanDetails" xlink:type="extended" id="i47e1d1ab0d624260bba8812e3b16585b_EmployeeBenefitPlanDetails"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/CommitmentsandContingencies" xlink:type="simple" xlink:href="anab-20201231.xsd#CommitmentsandContingencies"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/CommitmentsandContingencies" xlink:type="extended" id="i0e5def19fac0415994bc60cbc33a31eb_CommitmentsandContingencies"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/CommitmentsandContingenciesTables" xlink:type="simple" xlink:href="anab-20201231.xsd#CommitmentsandContingenciesTables"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/CommitmentsandContingenciesTables" xlink:type="extended" id="i56fc3532561c4c44aa3f5c062cdb25f7_CommitmentsandContingenciesTables"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/CommitmentsandContingenciesNarrativeDetails" xlink:type="simple" xlink:href="anab-20201231.xsd#CommitmentsandContingenciesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/CommitmentsandContingenciesNarrativeDetails" xlink:type="extended" id="i9b81a0f4f5a14fe88035926ca40705a3_CommitmentsandContingenciesNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_49875fbc-cfaa-4ba9-8bc8-1c8d017acf5f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnSaleOfPropertyPlantEquipment_cc799610-b454-46ad-ad2a-b0401cd10c39" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GainLossOnSaleOfPropertyPlantEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_49875fbc-cfaa-4ba9-8bc8-1c8d017acf5f" xlink:to="loc_us-gaap_GainLossOnSaleOfPropertyPlantEquipment_cc799610-b454-46ad-ad2a-b0401cd10c39" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_07afbb57-1a20-420e-9072-975ab571ddaa" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_49875fbc-cfaa-4ba9-8bc8-1c8d017acf5f" xlink:to="loc_us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_07afbb57-1a20-420e-9072-975ab571ddaa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeasesRentExpenseNet_85f28986-c164-4410-b57c-e4197c0efabf" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeasesRentExpenseNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_49875fbc-cfaa-4ba9-8bc8-1c8d017acf5f" xlink:to="loc_us-gaap_OperatingLeasesRentExpenseNet_85f28986-c164-4410-b57c-e4197c0efabf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AreaOfRealEstateProperty_e2dae85c-61bd-4116-b5fb-ab2b27fe8908" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AreaOfRealEstateProperty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_49875fbc-cfaa-4ba9-8bc8-1c8d017acf5f" xlink:to="loc_us-gaap_AreaOfRealEstateProperty_e2dae85c-61bd-4116-b5fb-ab2b27fe8908" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLeaseNotYetCommencedTermOfContract1_20b1b79e-1968-4a60-a4c4-af78520cac06" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLeaseNotYetCommencedTermOfContract1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_49875fbc-cfaa-4ba9-8bc8-1c8d017acf5f" xlink:to="loc_us-gaap_LesseeOperatingLeaseLeaseNotYetCommencedTermOfContract1_20b1b79e-1968-4a60-a4c4-af78520cac06" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLeaseNotYetCommencedRenewalTerm1_66053607-424d-4079-9cad-2c0d0f90c1dc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLeaseNotYetCommencedRenewalTerm1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_49875fbc-cfaa-4ba9-8bc8-1c8d017acf5f" xlink:to="loc_us-gaap_LesseeOperatingLeaseLeaseNotYetCommencedRenewalTerm1_66053607-424d-4079-9cad-2c0d0f90c1dc" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_LesseeOperatingLeaseLeaseNotYetCommencedOneTimeOptionToTerminateExpirationPeriod_abece0d6-1fa9-45cd-93c4-9072a58d336b" xlink:href="anab-20201231.xsd#anab_LesseeOperatingLeaseLeaseNotYetCommencedOneTimeOptionToTerminateExpirationPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_49875fbc-cfaa-4ba9-8bc8-1c8d017acf5f" xlink:to="loc_anab_LesseeOperatingLeaseLeaseNotYetCommencedOneTimeOptionToTerminateExpirationPeriod_abece0d6-1fa9-45cd-93c4-9072a58d336b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_RentPerSquareFoot_8d35802c-c11f-4ea2-b019-e92610918f8b" xlink:href="anab-20201231.xsd#anab_RentPerSquareFoot"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_49875fbc-cfaa-4ba9-8bc8-1c8d017acf5f" xlink:to="loc_anab_RentPerSquareFoot_8d35802c-c11f-4ea2-b019-e92610918f8b" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_AnnualRentIncreasePercent_6ab93f13-767f-4c75-b3d1-fee3a91a2cd1" xlink:href="anab-20201231.xsd#anab_AnnualRentIncreasePercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_49875fbc-cfaa-4ba9-8bc8-1c8d017acf5f" xlink:to="loc_anab_AnnualRentIncreasePercent_6ab93f13-767f-4c75-b3d1-fee3a91a2cd1" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidRent_fef181a6-45de-4cfc-90a9-7beac8d0b2cc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PrepaidRent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_49875fbc-cfaa-4ba9-8bc8-1c8d017acf5f" xlink:to="loc_us-gaap_PrepaidRent_fef181a6-45de-4cfc-90a9-7beac8d0b2cc" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecurityDeposit_728a2dd6-63f9-4e94-b1b2-d885c2c2caff" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SecurityDeposit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_49875fbc-cfaa-4ba9-8bc8-1c8d017acf5f" xlink:to="loc_us-gaap_SecurityDeposit_728a2dd6-63f9-4e94-b1b2-d885c2c2caff" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_CollaborationLicenseAgreementMaximumTerm_db9a95f4-0cb5-4768-97ad-70c921c09277" xlink:href="anab-20201231.xsd#anab_CollaborationLicenseAgreementMaximumTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_49875fbc-cfaa-4ba9-8bc8-1c8d017acf5f" xlink:to="loc_anab_CollaborationLicenseAgreementMaximumTerm_db9a95f4-0cb5-4768-97ad-70c921c09277" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_CollaborationLicenseAgreementUpfrontMilestoneAndRoyaltyExpense_01130607-53ff-4966-84ba-8de860546334" xlink:href="anab-20201231.xsd#anab_CollaborationLicenseAgreementUpfrontMilestoneAndRoyaltyExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_49875fbc-cfaa-4ba9-8bc8-1c8d017acf5f" xlink:to="loc_anab_CollaborationLicenseAgreementUpfrontMilestoneAndRoyaltyExpense_01130607-53ff-4966-84ba-8de860546334" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_PaymentsForUpfrontMilestoneAndRoyaltyPayments_1661bea6-d423-4057-a324-d1f783b4b379" xlink:href="anab-20201231.xsd#anab_PaymentsForUpfrontMilestoneAndRoyaltyPayments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_49875fbc-cfaa-4ba9-8bc8-1c8d017acf5f" xlink:to="loc_anab_PaymentsForUpfrontMilestoneAndRoyaltyPayments_1661bea6-d423-4057-a324-d1f783b4b379" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentDueInNextTwelveMonths_61401561-173a-4009-a6c8-8275395c79ec" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherCommitmentDueInNextTwelveMonths"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_49875fbc-cfaa-4ba9-8bc8-1c8d017acf5f" xlink:to="loc_us-gaap_OtherCommitmentDueInNextTwelveMonths_61401561-173a-4009-a6c8-8275395c79ec" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_OtherCommitmentsDueAfterYearOne_57f2b059-bcad-4b95-83f3-5c09c3c5baef" xlink:href="anab-20201231.xsd#anab_OtherCommitmentsDueAfterYearOne"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_49875fbc-cfaa-4ba9-8bc8-1c8d017acf5f" xlink:to="loc_anab_OtherCommitmentsDueAfterYearOne_57f2b059-bcad-4b95-83f3-5c09c3c5baef" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_CollaborationLicenseAgreementObligationPayablePeriod_ffae9e11-6180-41af-b936-c1895f084bf1" xlink:href="anab-20201231.xsd#anab_CollaborationLicenseAgreementObligationPayablePeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_49875fbc-cfaa-4ba9-8bc8-1c8d017acf5f" xlink:to="loc_anab_CollaborationLicenseAgreementObligationPayablePeriod_ffae9e11-6180-41af-b936-c1895f084bf1" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LettersOfCreditOutstandingAmount_ccef5693-183f-4057-a4ee-a124c1ed70f6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LettersOfCreditOutstandingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_49875fbc-cfaa-4ba9-8bc8-1c8d017acf5f" xlink:to="loc_us-gaap_LettersOfCreditOutstandingAmount_ccef5693-183f-4057-a4ee-a124c1ed70f6" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_5204de94-fc29-4802-81c5-0160fcfe7241" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_49875fbc-cfaa-4ba9-8bc8-1c8d017acf5f" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_5204de94-fc29-4802-81c5-0160fcfe7241" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_LeaseArrangementAxis_430f9016-253a-4e1d-b417-2b9e78920add" xlink:href="anab-20201231.xsd#anab_LeaseArrangementAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_5204de94-fc29-4802-81c5-0160fcfe7241" xlink:to="loc_anab_LeaseArrangementAxis_430f9016-253a-4e1d-b417-2b9e78920add" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_LeaseArrangementDomain_430f9016-253a-4e1d-b417-2b9e78920add_default" xlink:href="anab-20201231.xsd#anab_LeaseArrangementDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_anab_LeaseArrangementAxis_430f9016-253a-4e1d-b417-2b9e78920add" xlink:to="loc_anab_LeaseArrangementDomain_430f9016-253a-4e1d-b417-2b9e78920add_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_LeaseArrangementDomain_1ebe9a2e-f40c-4f44-9853-dfb98df11653" xlink:href="anab-20201231.xsd#anab_LeaseArrangementDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_anab_LeaseArrangementAxis_430f9016-253a-4e1d-b417-2b9e78920add" xlink:to="loc_anab_LeaseArrangementDomain_1ebe9a2e-f40c-4f44-9853-dfb98df11653" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_A10770WateridgeCircleSanDiegoCalifornia92121Member_28f65fad-96f3-4ad0-8cec-21ad8e873c09" xlink:href="anab-20201231.xsd#anab_A10770WateridgeCircleSanDiegoCalifornia92121Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_anab_LeaseArrangementDomain_1ebe9a2e-f40c-4f44-9853-dfb98df11653" xlink:to="loc_anab_A10770WateridgeCircleSanDiegoCalifornia92121Member_28f65fad-96f3-4ad0-8cec-21ad8e873c09" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_a38989b2-3684-406a-89cc-296c0a8b6da6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_5204de94-fc29-4802-81c5-0160fcfe7241" xlink:to="loc_us-gaap_CreditFacilityAxis_a38989b2-3684-406a-89cc-296c0a8b6da6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_a38989b2-3684-406a-89cc-296c0a8b6da6_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_a38989b2-3684-406a-89cc-296c0a8b6da6" xlink:to="loc_us-gaap_CreditFacilityDomain_a38989b2-3684-406a-89cc-296c0a8b6da6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_df580393-36f6-4ae4-844f-5bb4662463f8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_a38989b2-3684-406a-89cc-296c0a8b6da6" xlink:to="loc_us-gaap_CreditFacilityDomain_df580393-36f6-4ae4-844f-5bb4662463f8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StandbyLettersOfCreditMember_c77dc3dd-3425-4a99-8d2f-c79986b35306" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StandbyLettersOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_df580393-36f6-4ae4-844f-5bb4662463f8" xlink:to="loc_us-gaap_StandbyLettersOfCreditMember_c77dc3dd-3425-4a99-8d2f-c79986b35306" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/CommitmentsandContingenciesScheduleofROUAssetsandLeaseLiabilitiesDetails" xlink:type="simple" xlink:href="anab-20201231.xsd#CommitmentsandContingenciesScheduleofROUAssetsandLeaseLiabilitiesDetails"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/CommitmentsandContingenciesScheduleofROUAssetsandLeaseLiabilitiesDetails" xlink:type="extended" id="i1d1c69350f614f3ca024eca1528a5094_CommitmentsandContingenciesScheduleofROUAssetsandLeaseLiabilitiesDetails"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/CommitmentsandContingenciesCostsinCashFlowStatementDetails" xlink:type="simple" xlink:href="anab-20201231.xsd#CommitmentsandContingenciesCostsinCashFlowStatementDetails"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/CommitmentsandContingenciesCostsinCashFlowStatementDetails" xlink:type="extended" id="i6541a8630e4d4354b6890b7d8d735aea_CommitmentsandContingenciesCostsinCashFlowStatementDetails"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/CommitmentsandContingenciesScheduleofFutureMinimumAnnualObligationsunderOperatingLeasesDetails" xlink:type="simple" xlink:href="anab-20201231.xsd#CommitmentsandContingenciesScheduleofFutureMinimumAnnualObligationsunderOperatingLeasesDetails"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/CommitmentsandContingenciesScheduleofFutureMinimumAnnualObligationsunderOperatingLeasesDetails" xlink:type="extended" id="ibc0544ad227045f3b7e78126d5f31349_CommitmentsandContingenciesScheduleofFutureMinimumAnnualObligationsunderOperatingLeasesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_a97e25ce-571b-4be7-8a7a-68085e4f8dbc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths_970dbde0-6f95-4ebc-b8da-de96bcbb9d8a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_a97e25ce-571b-4be7-8a7a-68085e4f8dbc" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths_970dbde0-6f95-4ebc-b8da-de96bcbb9d8a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_8b7a8b89-9fc7-4d13-9e79-3c1379e7e523" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_a97e25ce-571b-4be7-8a7a-68085e4f8dbc" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_8b7a8b89-9fc7-4d13-9e79-3c1379e7e523" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_d3aab7d3-8302-413f-9203-358267c25074" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_a97e25ce-571b-4be7-8a7a-68085e4f8dbc" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_d3aab7d3-8302-413f-9203-358267c25074" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour_89f8980a-6cdd-435d-b353-a61a1753caa0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_a97e25ce-571b-4be7-8a7a-68085e4f8dbc" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour_89f8980a-6cdd-435d-b353-a61a1753caa0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive_7dd454e0-78bc-4f20-9c59-3a55e41bedef" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_a97e25ce-571b-4be7-8a7a-68085e4f8dbc" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive_7dd454e0-78bc-4f20-9c59-3a55e41bedef" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive_e1d65a23-0bce-4dbd-8538-020824ea5fc8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_a97e25ce-571b-4be7-8a7a-68085e4f8dbc" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive_e1d65a23-0bce-4dbd-8538-020824ea5fc8" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_da1d14f6-74bc-478b-b86a-c41de1589443" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_a97e25ce-571b-4be7-8a7a-68085e4f8dbc" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_da1d14f6-74bc-478b-b86a-c41de1589443" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_fe5fd1e8-8384-454a-81f4-79d85e66f124" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_a97e25ce-571b-4be7-8a7a-68085e4f8dbc" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_fe5fd1e8-8384-454a-81f4-79d85e66f124" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiability_41834984-997a-44b7-9716-3fef9cd00a15" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_a97e25ce-571b-4be7-8a7a-68085e4f8dbc" xlink:to="loc_us-gaap_OperatingLeaseLiability_41834984-997a-44b7-9716-3fef9cd00a15" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_854b4b15-c1a8-47f5-9081-604b4041a959" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_a97e25ce-571b-4be7-8a7a-68085e4f8dbc" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_854b4b15-c1a8-47f5-9081-604b4041a959" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_LeaseArrangementAxis_3222b978-c387-418d-a741-8b71c42740d0" xlink:href="anab-20201231.xsd#anab_LeaseArrangementAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_854b4b15-c1a8-47f5-9081-604b4041a959" xlink:to="loc_anab_LeaseArrangementAxis_3222b978-c387-418d-a741-8b71c42740d0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_LeaseArrangementDomain_3222b978-c387-418d-a741-8b71c42740d0_default" xlink:href="anab-20201231.xsd#anab_LeaseArrangementDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_anab_LeaseArrangementAxis_3222b978-c387-418d-a741-8b71c42740d0" xlink:to="loc_anab_LeaseArrangementDomain_3222b978-c387-418d-a741-8b71c42740d0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_LeaseArrangementDomain_7256abc9-7c20-4aaa-9863-7abf485168d8" xlink:href="anab-20201231.xsd#anab_LeaseArrangementDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_anab_LeaseArrangementAxis_3222b978-c387-418d-a741-8b71c42740d0" xlink:to="loc_anab_LeaseArrangementDomain_7256abc9-7c20-4aaa-9863-7abf485168d8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_A10770WateridgeCircleSanDiegoCalifornia92121Member_a88604ff-651e-4012-9861-2708ae87a61e" xlink:href="anab-20201231.xsd#anab_A10770WateridgeCircleSanDiegoCalifornia92121Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_anab_LeaseArrangementDomain_7256abc9-7c20-4aaa-9863-7abf485168d8" xlink:to="loc_anab_A10770WateridgeCircleSanDiegoCalifornia92121Member_a88604ff-651e-4012-9861-2708ae87a61e" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/IncomeTaxes" xlink:type="simple" xlink:href="anab-20201231.xsd#IncomeTaxes"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/IncomeTaxes" xlink:type="extended" id="i25b9fa1ee68645e098ee9be5dd531ff1_IncomeTaxes"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/IncomeTaxesTables" xlink:type="simple" xlink:href="anab-20201231.xsd#IncomeTaxesTables"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/IncomeTaxesTables" xlink:type="extended" id="iaa7e38b8555c458ea0dcbd4f6134dc78_IncomeTaxesTables"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/IncomeTaxesComponentsofincomelossbeforeincometaxprovisionbenefitDetails" xlink:type="simple" xlink:href="anab-20201231.xsd#IncomeTaxesComponentsofincomelossbeforeincometaxprovisionbenefitDetails"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/IncomeTaxesComponentsofincomelossbeforeincometaxprovisionbenefitDetails" xlink:type="extended" id="i1e78911b233c443ba5eb51b93f2f92ed_IncomeTaxesComponentsofincomelossbeforeincometaxprovisionbenefitDetails"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/IncomeTaxesDeferredtaxassetsandliabilitiesDetails" xlink:type="simple" xlink:href="anab-20201231.xsd#IncomeTaxesDeferredtaxassetsandliabilitiesDetails"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/IncomeTaxesDeferredtaxassetsandliabilitiesDetails" xlink:type="extended" id="i9fb1aebaa1c34bc499d95ff1a9a6d78d_IncomeTaxesDeferredtaxassetsandliabilitiesDetails"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/IncomeTaxesAdditionalinformationDetails" xlink:type="simple" xlink:href="anab-20201231.xsd#IncomeTaxesAdditionalinformationDetails"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/IncomeTaxesAdditionalinformationDetails" xlink:type="extended" id="i33c0e83249264f328337d27a1b515666_IncomeTaxesAdditionalinformationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLossCarryforwardsLineItems_f617e0e9-62e6-48a7-ad26-8a570c6e00fc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLossCarryforwardsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLossCarryforwards_622ad00e-4edb-4d73-9c34-78b9e55c1934" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLossCarryforwards"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_f617e0e9-62e6-48a7-ad26-8a570c6e00fc" xlink:to="loc_us-gaap_OperatingLossCarryforwards_622ad00e-4edb-4d73-9c34-78b9e55c1934" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxCreditCarryforwardAmount_9c9e73d2-d923-464a-bb31-dbe98976128e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TaxCreditCarryforwardAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_f617e0e9-62e6-48a7-ad26-8a570c6e00fc" xlink:to="loc_us-gaap_TaxCreditCarryforwardAmount_9c9e73d2-d923-464a-bb31-dbe98976128e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_OperatingLossCarryforwardsLimitationsOnUseAmount_16953f99-4527-436f-b4aa-054700c550e0" xlink:href="anab-20201231.xsd#anab_OperatingLossCarryforwardsLimitationsOnUseAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_f617e0e9-62e6-48a7-ad26-8a570c6e00fc" xlink:to="loc_anab_OperatingLossCarryforwardsLimitationsOnUseAmount_16953f99-4527-436f-b4aa-054700c550e0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_TaxCreditCarryforwardLimitationsOnUseAmount_1f623719-61e6-4c52-9fc6-95225c791de6" xlink:href="anab-20201231.xsd#anab_TaxCreditCarryforwardLimitationsOnUseAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_f617e0e9-62e6-48a7-ad26-8a570c6e00fc" xlink:to="loc_anab_TaxCreditCarryforwardLimitationsOnUseAmount_1f623719-61e6-4c52-9fc6-95225c791de6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate_859d5789-eb61-421b-9b11-c4931fabae57" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_f617e0e9-62e6-48a7-ad26-8a570c6e00fc" xlink:to="loc_us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate_859d5789-eb61-421b-9b11-c4931fabae57" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense_f8805448-64db-4196-8b21-3b1db484b764" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_f617e0e9-62e6-48a7-ad26-8a570c6e00fc" xlink:to="loc_us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense_f8805448-64db-4196-8b21-3b1db484b764" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLossCarryforwardsTable_87179950-7859-4598-9e24-ea5cb24f1580" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLossCarryforwardsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_f617e0e9-62e6-48a7-ad26-8a570c6e00fc" xlink:to="loc_us-gaap_OperatingLossCarryforwardsTable_87179950-7859-4598-9e24-ea5cb24f1580" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityAxis_d5e2a5ec-62de-414c-b1fe-091c64c39c58" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxAuthorityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_OperatingLossCarryforwardsTable_87179950-7859-4598-9e24-ea5cb24f1580" xlink:to="loc_us-gaap_IncomeTaxAuthorityAxis_d5e2a5ec-62de-414c-b1fe-091c64c39c58" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_d5e2a5ec-62de-414c-b1fe-091c64c39c58_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxAuthorityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_d5e2a5ec-62de-414c-b1fe-091c64c39c58" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_d5e2a5ec-62de-414c-b1fe-091c64c39c58_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_2f4c5575-fe21-45a1-a91b-c4015c67bdec" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxAuthorityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_d5e2a5ec-62de-414c-b1fe-091c64c39c58" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_2f4c5575-fe21-45a1-a91b-c4015c67bdec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DomesticCountryMember_6e69135c-c6fd-42b8-ab36-a798c64261d5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DomesticCountryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_2f4c5575-fe21-45a1-a91b-c4015c67bdec" xlink:to="loc_us-gaap_DomesticCountryMember_6e69135c-c6fd-42b8-ab36-a798c64261d5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StateAndLocalJurisdictionMember_c5972ee6-484a-44d6-b5d3-36339eb8f8aa" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StateAndLocalJurisdictionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_2f4c5575-fe21-45a1-a91b-c4015c67bdec" xlink:to="loc_us-gaap_StateAndLocalJurisdictionMember_c5972ee6-484a-44d6-b5d3-36339eb8f8aa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCountryMember_79fa0641-dbf2-4f95-9d61-9207ba46d8b7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ForeignCountryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_2f4c5575-fe21-45a1-a91b-c4015c67bdec" xlink:to="loc_us-gaap_ForeignCountryMember_79fa0641-dbf2-4f95-9d61-9207ba46d8b7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxCreditCarryforwardAxis_86749e68-9844-45ae-9d7c-54e61b4d0aa3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TaxCreditCarryforwardAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_OperatingLossCarryforwardsTable_87179950-7859-4598-9e24-ea5cb24f1580" xlink:to="loc_us-gaap_TaxCreditCarryforwardAxis_86749e68-9844-45ae-9d7c-54e61b4d0aa3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxCreditCarryforwardNameDomain_86749e68-9844-45ae-9d7c-54e61b4d0aa3_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TaxCreditCarryforwardNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_TaxCreditCarryforwardAxis_86749e68-9844-45ae-9d7c-54e61b4d0aa3" xlink:to="loc_us-gaap_TaxCreditCarryforwardNameDomain_86749e68-9844-45ae-9d7c-54e61b4d0aa3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxCreditCarryforwardNameDomain_82e319c0-6a6d-4af2-9036-fa6023b697d4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TaxCreditCarryforwardNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_TaxCreditCarryforwardAxis_86749e68-9844-45ae-9d7c-54e61b4d0aa3" xlink:to="loc_us-gaap_TaxCreditCarryforwardNameDomain_82e319c0-6a6d-4af2-9036-fa6023b697d4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchMember_9d62fd88-b025-4703-9987-ce992981eb63" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ResearchMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TaxCreditCarryforwardNameDomain_82e319c0-6a6d-4af2-9036-fa6023b697d4" xlink:to="loc_us-gaap_ResearchMember_9d62fd88-b025-4703-9987-ce992981eb63" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxPeriodAxis_a60a5c42-1b3f-401e-a8fd-d1fc2d56b955" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TaxPeriodAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_OperatingLossCarryforwardsTable_87179950-7859-4598-9e24-ea5cb24f1580" xlink:to="loc_us-gaap_TaxPeriodAxis_a60a5c42-1b3f-401e-a8fd-d1fc2d56b955" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxPeriodDomain_a60a5c42-1b3f-401e-a8fd-d1fc2d56b955_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TaxPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_TaxPeriodAxis_a60a5c42-1b3f-401e-a8fd-d1fc2d56b955" xlink:to="loc_us-gaap_TaxPeriodDomain_a60a5c42-1b3f-401e-a8fd-d1fc2d56b955_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxPeriodDomain_5eb73d07-e8af-4689-beb5-02484065bf53" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TaxPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_TaxPeriodAxis_a60a5c42-1b3f-401e-a8fd-d1fc2d56b955" xlink:to="loc_us-gaap_TaxPeriodDomain_5eb73d07-e8af-4689-beb5-02484065bf53" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_TaxYear2018AndAfterMember_3edec381-3f24-42a5-be53-484d4ef5c3e9" xlink:href="anab-20201231.xsd#anab_TaxYear2018AndAfterMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TaxPeriodDomain_5eb73d07-e8af-4689-beb5-02484065bf53" xlink:to="loc_anab_TaxYear2018AndAfterMember_3edec381-3f24-42a5-be53-484d4ef5c3e9" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/IncomeTaxesReconciliationofincometaxesDetails" xlink:type="simple" xlink:href="anab-20201231.xsd#IncomeTaxesReconciliationofincometaxesDetails"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/IncomeTaxesReconciliationofincometaxesDetails" xlink:type="extended" id="i44ebc210116e496784946e678bdaff8c_IncomeTaxesReconciliationofincometaxesDetails"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/IncomeTaxesUnrecognizedtaxbenefitsDetails" xlink:type="simple" xlink:href="anab-20201231.xsd#IncomeTaxesUnrecognizedtaxbenefitsDetails"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/IncomeTaxesUnrecognizedtaxbenefitsDetails" xlink:type="extended" id="i3d4012ee539f4c199a9302cbcc4e537b_IncomeTaxesUnrecognizedtaxbenefitsDetails"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/SubsequentEvent" xlink:type="simple" xlink:href="anab-20201231.xsd#SubsequentEvent"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/SubsequentEvent" xlink:type="extended" id="iedcb77291c6c4eaa9ee1b69220c8ed44_SubsequentEvent"/>
  <link:roleRef roleURI="http://www.anaptysbio.com/role/SubsequentEventDetails" xlink:type="simple" xlink:href="anab-20201231.xsd#SubsequentEventDetails"/>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/SubsequentEventDetails" xlink:type="extended" id="iaeda3cc246d84de09122cb7279bd02bb_SubsequentEventDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventLineItems_093ee597-3b3b-4123-86b9-b8180306958a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_RevenueRecognizedMilestoneMethodMilestonePaymentEarned_66a7d807-7324-4b5c-a813-ddba1f735b38" xlink:href="anab-20201231.xsd#anab_RevenueRecognizedMilestoneMethodMilestonePaymentEarned"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_093ee597-3b3b-4123-86b9-b8180306958a" xlink:to="loc_anab_RevenueRecognizedMilestoneMethodMilestonePaymentEarned_66a7d807-7324-4b5c-a813-ddba1f735b38" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTable_b88d44ac-0e64-4e2f-b5d5-39ef20103d02" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SubsequentEventLineItems_093ee597-3b3b-4123-86b9-b8180306958a" xlink:to="loc_us-gaap_SubsequentEventTable_b88d44ac-0e64-4e2f-b5d5-39ef20103d02" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementScenarioAxis_0dae48fa-9340-499a-be54-a4bc51ec8035" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_StatementScenarioAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_b88d44ac-0e64-4e2f-b5d5-39ef20103d02" xlink:to="loc_srt_StatementScenarioAxis_0dae48fa-9340-499a-be54-a4bc51ec8035" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_0dae48fa-9340-499a-be54-a4bc51ec8035_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementScenarioAxis_0dae48fa-9340-499a-be54-a4bc51ec8035" xlink:to="loc_srt_ScenarioUnspecifiedDomain_0dae48fa-9340-499a-be54-a4bc51ec8035_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_6ceb6c2a-97c7-49c5-950f-be7d79592719" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementScenarioAxis_0dae48fa-9340-499a-be54-a4bc51ec8035" xlink:to="loc_srt_ScenarioUnspecifiedDomain_6ceb6c2a-97c7-49c5-950f-be7d79592719" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioForecastMember_71aa4ea0-dda1-43ab-baca-c5f9019e4c3a" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ScenarioForecastMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ScenarioUnspecifiedDomain_6ceb6c2a-97c7-49c5-950f-be7d79592719" xlink:to="loc_srt_ScenarioForecastMember_71aa4ea0-dda1-43ab-baca-c5f9019e4c3a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_b6a4469f-c3ec-4a7c-ac47-4cbdb41c726d" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_b88d44ac-0e64-4e2f-b5d5-39ef20103d02" xlink:to="loc_srt_CounterpartyNameAxis_b6a4469f-c3ec-4a7c-ac47-4cbdb41c726d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_b6a4469f-c3ec-4a7c-ac47-4cbdb41c726d_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_b6a4469f-c3ec-4a7c-ac47-4cbdb41c726d" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_b6a4469f-c3ec-4a7c-ac47-4cbdb41c726d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_7343a84f-759f-45ae-9b1a-c696eeb3675a" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_b6a4469f-c3ec-4a7c-ac47-4cbdb41c726d" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_7343a84f-759f-45ae-9b1a-c696eeb3675a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_TESAROInc.AndTESARODevelopmentInc.Member_e5e9aaf1-dfc3-4993-b0e4-1e037c71ceb0" xlink:href="anab-20201231.xsd#anab_TESAROInc.AndTESARODevelopmentInc.Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_7343a84f-759f-45ae-9b1a-c696eeb3675a" xlink:to="loc_anab_TESAROInc.AndTESARODevelopmentInc.Member_e5e9aaf1-dfc3-4993-b0e4-1e037c71ceb0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_f612d39f-e677-41ce-86f0-9b85b47f5004" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_b88d44ac-0e64-4e2f-b5d5-39ef20103d02" xlink:to="loc_srt_ProductOrServiceAxis_f612d39f-e677-41ce-86f0-9b85b47f5004" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_f612d39f-e677-41ce-86f0-9b85b47f5004_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_f612d39f-e677-41ce-86f0-9b85b47f5004" xlink:to="loc_srt_ProductsAndServicesDomain_f612d39f-e677-41ce-86f0-9b85b47f5004_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_49d06e8a-3b18-4d02-b36f-9745207a0b64" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_f612d39f-e677-41ce-86f0-9b85b47f5004" xlink:to="loc_srt_ProductsAndServicesDomain_49d06e8a-3b18-4d02-b36f-9745207a0b64" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_AnaptysBiogeneratedAntiPD1AntagonistAntibodyTSR042Member_612d8cac-1e8d-49aa-a9c1-d68d02ef1e1f" xlink:href="anab-20201231.xsd#anab_AnaptysBiogeneratedAntiPD1AntagonistAntibodyTSR042Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_49d06e8a-3b18-4d02-b36f-9745207a0b64" xlink:to="loc_anab_AnaptysBiogeneratedAntiPD1AntagonistAntibodyTSR042Member_612d8cac-1e8d-49aa-a9c1-d68d02ef1e1f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfArrangementAxis_cd1f91bd-feb7-4ca6-a75f-801021897152" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TypeOfArrangementAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_b88d44ac-0e64-4e2f-b5d5-39ef20103d02" xlink:to="loc_us-gaap_TypeOfArrangementAxis_cd1f91bd-feb7-4ca6-a75f-801021897152" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_cd1f91bd-feb7-4ca6-a75f-801021897152_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ArrangementsAndNonarrangementTransactionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_TypeOfArrangementAxis_cd1f91bd-feb7-4ca6-a75f-801021897152" xlink:to="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_cd1f91bd-feb7-4ca6-a75f-801021897152_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_2902fd39-949b-4b1b-ad13-b1f527fa53c5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ArrangementsAndNonarrangementTransactionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_TypeOfArrangementAxis_cd1f91bd-feb7-4ca6-a75f-801021897152" xlink:to="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_2902fd39-949b-4b1b-ad13-b1f527fa53c5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_anab_InVivoToxicologyStudiesMember_91c11dbb-eae0-4169-bd44-05a98c70a2d7" xlink:href="anab-20201231.xsd#anab_InVivoToxicologyStudiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_2902fd39-949b-4b1b-ad13-b1f527fa53c5" xlink:to="loc_anab_InVivoToxicologyStudiesMember_91c11dbb-eae0-4169-bd44-05a98c70a2d7" xlink:type="arc" order="0"/>
  </link:definitionLink>
</link:linkbase>
