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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2023 Workiva-->
<!--r:0c6df27e-9e11-42f6-9346-97c8d2879b1f,g:14310197-22f1-4c7a-81c2-16779dd2afe3-->
<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.ngmbio.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETS" xlink:type="simple" xlink:href="ngm-20230630.xsd#CONDENSEDCONSOLIDATEDBALANCESHEETS"/>
  <link:definitionLink xlink:role="http://www.ngmbio.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETS" xlink:type="extended" id="id5d23fa3bc914eaeb524566f080b2c2f_CONDENSEDCONSOLIDATEDBALANCESHEETS">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_40a26d7b-34c4-4cde-aaa3-65ee96a22183" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract_d3390831-2e2d-4aeb-b6f0-fce938717b10" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_40a26d7b-34c4-4cde-aaa3-65ee96a22183" xlink:to="loc_us-gaap_AssetsAbstract_d3390831-2e2d-4aeb-b6f0-fce938717b10" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrentAbstract_c4ad56de-2885-418a-a2b0-f0c603e8d8bb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsCurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_d3390831-2e2d-4aeb-b6f0-fce938717b10" xlink:to="loc_us-gaap_AssetsCurrentAbstract_c4ad56de-2885-418a-a2b0-f0c603e8d8bb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_32d2f5df-069a-4d6f-b926-dc3c14309172" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_c4ad56de-2885-418a-a2b0-f0c603e8d8bb" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_32d2f5df-069a-4d6f-b926-dc3c14309172" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermInvestments_ddcfaad2-7249-4e91-ac8e-4690d3393575" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShortTermInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_c4ad56de-2885-418a-a2b0-f0c603e8d8bb" xlink:to="loc_us-gaap_ShortTermInvestments_ddcfaad2-7249-4e91-ac8e-4690d3393575" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNetCurrent_5bc020dc-5532-4976-8225-22c980af67c8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccountsReceivableNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_c4ad56de-2885-418a-a2b0-f0c603e8d8bb" xlink:to="loc_us-gaap_AccountsReceivableNetCurrent_5bc020dc-5532-4976-8225-22c980af67c8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_22183de2-ba06-4ab7-beb9-851bd115b07a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PrepaidExpenseAndOtherAssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_c4ad56de-2885-418a-a2b0-f0c603e8d8bb" xlink:to="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_22183de2-ba06-4ab7-beb9-851bd115b07a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashCurrent_aae1931f-fc1b-4688-a1ad-b495093fa7f1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedCashCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_c4ad56de-2885-418a-a2b0-f0c603e8d8bb" xlink:to="loc_us-gaap_RestrictedCashCurrent_aae1931f-fc1b-4688-a1ad-b495093fa7f1" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrent_db538f39-ea77-4d70-a04e-7e133ad1bbcb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_c4ad56de-2885-418a-a2b0-f0c603e8d8bb" xlink:to="loc_us-gaap_AssetsCurrent_db538f39-ea77-4d70-a04e-7e133ad1bbcb" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_8e09e27b-8efe-4fa9-a00e-20199bff99aa" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_d3390831-2e2d-4aeb-b6f0-fce938717b10" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_8e09e27b-8efe-4fa9-a00e-20199bff99aa" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset_0bbccd75-3e9d-4b7b-9324-8b5a2ecf28f8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingLeaseRightOfUseAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_d3390831-2e2d-4aeb-b6f0-fce938717b10" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAsset_0bbccd75-3e9d-4b7b-9324-8b5a2ecf28f8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashNoncurrent_13089fc2-9cea-47e4-827f-eb8cf26ab2ab" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedCashNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_d3390831-2e2d-4aeb-b6f0-fce938717b10" xlink:to="loc_us-gaap_RestrictedCashNoncurrent_13089fc2-9cea-47e4-827f-eb8cf26ab2ab" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsNoncurrent_dd347a09-e6eb-41c6-a3fe-ceb62d0565b7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherAssetsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_d3390831-2e2d-4aeb-b6f0-fce938717b10" xlink:to="loc_us-gaap_OtherAssetsNoncurrent_dd347a09-e6eb-41c6-a3fe-ceb62d0565b7" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_baf3f991-33dc-489a-9f22-70744b66ab6a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_d3390831-2e2d-4aeb-b6f0-fce938717b10" xlink:to="loc_us-gaap_Assets_baf3f991-33dc-489a-9f22-70744b66ab6a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_00761269-a840-42eb-bbb2-255c38f61264" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_40a26d7b-34c4-4cde-aaa3-65ee96a22183" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_00761269-a840-42eb-bbb2-255c38f61264" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrentAbstract_88eaaef0-6af8-4446-8278-7e015d5d9d1c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LiabilitiesCurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_00761269-a840-42eb-bbb2-255c38f61264" xlink:to="loc_us-gaap_LiabilitiesCurrentAbstract_88eaaef0-6af8-4446-8278-7e015d5d9d1c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableCurrent_c249d044-694d-4347-86ae-433462772840" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccountsPayableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_88eaaef0-6af8-4446-8278-7e015d5d9d1c" xlink:to="loc_us-gaap_AccountsPayableCurrent_c249d044-694d-4347-86ae-433462772840" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedLiabilitiesCurrent_18f24e28-70e9-42d2-90e1-9ab933d70b8a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccruedLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_88eaaef0-6af8-4446-8278-7e015d5d9d1c" xlink:to="loc_us-gaap_AccruedLiabilitiesCurrent_18f24e28-70e9-42d2-90e1-9ab933d70b8a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityCurrent_618c0d78-001d-4c4b-89c6-dabc0b8a8fe5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingLeaseLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_88eaaef0-6af8-4446-8278-7e015d5d9d1c" xlink:to="loc_us-gaap_OperatingLeaseLiabilityCurrent_618c0d78-001d-4c4b-89c6-dabc0b8a8fe5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityCurrent_3df7c87c-f5cf-45a3-bdf4-2f1f66590436" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ContractWithCustomerLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_88eaaef0-6af8-4446-8278-7e015d5d9d1c" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityCurrent_3df7c87c-f5cf-45a3-bdf4-2f1f66590436" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrent_cf70f432-6d1f-49ba-bdaf-98ff7effdced" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_88eaaef0-6af8-4446-8278-7e015d5d9d1c" xlink:to="loc_us-gaap_LiabilitiesCurrent_cf70f432-6d1f-49ba-bdaf-98ff7effdced" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_5a7255db-01bd-4ca8-95be-c122112e6147" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Liabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_00761269-a840-42eb-bbb2-255c38f61264" xlink:to="loc_us-gaap_Liabilities_5a7255db-01bd-4ca8-95be-c122112e6147" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsAndContingencies_3da1f5ed-d1ef-46e9-bad4-7955f9989bd8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommitmentsAndContingencies"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_00761269-a840-42eb-bbb2-255c38f61264" xlink:to="loc_us-gaap_CommitmentsAndContingencies_3da1f5ed-d1ef-46e9-bad4-7955f9989bd8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityAbstract_531ffba3-a1b3-4025-9859-82ab36aa03f3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_00761269-a840-42eb-bbb2-255c38f61264" xlink:to="loc_us-gaap_StockholdersEquityAbstract_531ffba3-a1b3-4025-9859-82ab36aa03f3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockValue_3387a1dd-cfb5-4895-8264-c2a33f407624" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PreferredStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_531ffba3-a1b3-4025-9859-82ab36aa03f3" xlink:to="loc_us-gaap_PreferredStockValue_3387a1dd-cfb5-4895-8264-c2a33f407624" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockValue_774f55c1-e364-4bf7-953f-947254fa65d4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_531ffba3-a1b3-4025-9859-82ab36aa03f3" xlink:to="loc_us-gaap_CommonStockValue_774f55c1-e364-4bf7-953f-947254fa65d4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalCommonStock_8248e850-102d-4861-8cfb-a67a92a30b9b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdditionalPaidInCapitalCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_531ffba3-a1b3-4025-9859-82ab36aa03f3" xlink:to="loc_us-gaap_AdditionalPaidInCapitalCommonStock_8248e850-102d-4861-8cfb-a67a92a30b9b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_6892b91a-4a1c-4a02-b961-fd3e1250f6f7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_531ffba3-a1b3-4025-9859-82ab36aa03f3" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_6892b91a-4a1c-4a02-b961-fd3e1250f6f7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_0799344d-034a-4373-a012-4e8f6925ea1c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_531ffba3-a1b3-4025-9859-82ab36aa03f3" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_0799344d-034a-4373-a012-4e8f6925ea1c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_aa7953e6-44e6-4c91-99e0-8bf0609f25a6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_531ffba3-a1b3-4025-9859-82ab36aa03f3" xlink:to="loc_us-gaap_StockholdersEquity_aa7953e6-44e6-4c91-99e0-8bf0609f25a6" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_0cc110e1-c2aa-41e3-b22b-bce06c837408" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LiabilitiesAndStockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_00761269-a840-42eb-bbb2-255c38f61264" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquity_0cc110e1-c2aa-41e3-b22b-bce06c837408" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_fac4de10-4d70-48fc-af83-df15dff2d461" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_40a26d7b-34c4-4cde-aaa3-65ee96a22183" xlink:to="loc_us-gaap_StatementTable_fac4de10-4d70-48fc-af83-df15dff2d461" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_8edf01d5-a64b-42a9-b65e-fe3a80320aec" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_fac4de10-4d70-48fc-af83-df15dff2d461" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_8edf01d5-a64b-42a9-b65e-fe3a80320aec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_8edf01d5-a64b-42a9-b65e-fe3a80320aec_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_8edf01d5-a64b-42a9-b65e-fe3a80320aec" xlink:to="loc_us-gaap_RelatedPartyDomain_8edf01d5-a64b-42a9-b65e-fe3a80320aec_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_1fda6a9d-d57e-49fa-ae12-5941f703b990" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_8edf01d5-a64b-42a9-b65e-fe3a80320aec" xlink:to="loc_us-gaap_RelatedPartyDomain_1fda6a9d-d57e-49fa-ae12-5941f703b990" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AffiliatedEntityMember_6eebc053-aa3e-44bf-931d-4cc09a2283f3" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_AffiliatedEntityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_1fda6a9d-d57e-49fa-ae12-5941f703b990" xlink:to="loc_srt_AffiliatedEntityMember_6eebc053-aa3e-44bf-931d-4cc09a2283f3" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ngmbio.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITY" xlink:type="simple" xlink:href="ngm-20230630.xsd#CONDENSEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITY"/>
  <link:definitionLink xlink:role="http://www.ngmbio.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITY" xlink:type="extended" id="i9db865c0c64f48b3bcd2aa925ebfc71c_CONDENSEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITY">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_d300c8ca-05e5-4996-a5cb-48d935d02ddc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0141f2c0-9346-4bfd-b3fc-011588f7bda9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_d300c8ca-05e5-4996-a5cb-48d935d02ddc" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0141f2c0-9346-4bfd-b3fc-011588f7bda9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesOutstanding_ca35b4dc-bcd8-4945-9f31-18ab970ecd5a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0141f2c0-9346-4bfd-b3fc-011588f7bda9" xlink:to="loc_us-gaap_SharesOutstanding_ca35b4dc-bcd8-4945-9f31-18ab970ecd5a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_e775db6c-1644-42b1-b77d-85f07a1bfd87" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0141f2c0-9346-4bfd-b3fc-011588f7bda9" xlink:to="loc_us-gaap_StockholdersEquity_e775db6c-1644-42b1-b77d-85f07a1bfd87" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_StockIssuedDuringPeriodSharesIssuanceOfUnderOpenMarketAgreement_ca050bad-3ef3-4c96-bc72-4d578e1d6a91" xlink:href="ngm-20230630.xsd#ngm_StockIssuedDuringPeriodSharesIssuanceOfUnderOpenMarketAgreement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0141f2c0-9346-4bfd-b3fc-011588f7bda9" xlink:to="loc_ngm_StockIssuedDuringPeriodSharesIssuanceOfUnderOpenMarketAgreement_ca050bad-3ef3-4c96-bc72-4d578e1d6a91" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_StockIssuedDuringPeriodValueIssuanceOfUnderOpenMarketAgreement_8641d03c-ecb2-4e29-949c-89c713f4183b" xlink:href="ngm-20230630.xsd#ngm_StockIssuedDuringPeriodValueIssuanceOfUnderOpenMarketAgreement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0141f2c0-9346-4bfd-b3fc-011588f7bda9" xlink:to="loc_ngm_StockIssuedDuringPeriodValueIssuanceOfUnderOpenMarketAgreement_8641d03c-ecb2-4e29-949c-89c713f4183b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_1ad45f8c-54ea-40af-b134-e9b0402b6a74" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0141f2c0-9346-4bfd-b3fc-011588f7bda9" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_1ad45f8c-54ea-40af-b134-e9b0402b6a74" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan_6f7b72ba-8dfd-4d3e-b6d7-0a45d2457a78" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0141f2c0-9346-4bfd-b3fc-011588f7bda9" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan_6f7b72ba-8dfd-4d3e-b6d7-0a45d2457a78" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_3bb0c7bc-4bc9-4af7-9f7c-ff113605ef5d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0141f2c0-9346-4bfd-b3fc-011588f7bda9" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_3bb0c7bc-4bc9-4af7-9f7c-ff113605ef5d" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_dbeae27d-8d9d-4fd0-a533-1720dc560e2e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0141f2c0-9346-4bfd-b3fc-011588f7bda9" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_dbeae27d-8d9d-4fd0-a533-1720dc560e2e" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeBenefitPlan_91463e4e-dd84-414a-a888-4bcc2199dfd3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesEmployeeBenefitPlan"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0141f2c0-9346-4bfd-b3fc-011588f7bda9" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeBenefitPlan_91463e4e-dd84-414a-a888-4bcc2199dfd3" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueEmployeeBenefitPlan_4cb3fd8d-8037-4db7-9a3a-873aed2e7601" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodValueEmployeeBenefitPlan"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0141f2c0-9346-4bfd-b3fc-011588f7bda9" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueEmployeeBenefitPlan_4cb3fd8d-8037-4db7-9a3a-873aed2e7601" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_2815c4d9-3045-4f5a-9059-742fd66bc06b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0141f2c0-9346-4bfd-b3fc-011588f7bda9" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_2815c4d9-3045-4f5a-9059-742fd66bc06b" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax_e2283184-36d6-4142-806d-40cd626b437c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0141f2c0-9346-4bfd-b3fc-011588f7bda9" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax_e2283184-36d6-4142-806d-40cd626b437c" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_28192ecf-cf44-4987-9fd9-9a331cfc88a3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0141f2c0-9346-4bfd-b3fc-011588f7bda9" xlink:to="loc_us-gaap_NetIncomeLoss_28192ecf-cf44-4987-9fd9-9a331cfc88a3" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesOutstanding_3a6f0908-1c9e-4658-8efe-5155c01025a7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_1fcd1d6e-cf70-4a63-8290-50185a56cc48" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_6a6c85dd-1b15-4a13-96e9-c15079fc52a9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_d300c8ca-05e5-4996-a5cb-48d935d02ddc" xlink:to="loc_us-gaap_StatementTable_6a6c85dd-1b15-4a13-96e9-c15079fc52a9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_c3e06ac4-c59c-452f-a533-acf8521c617b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_6a6c85dd-1b15-4a13-96e9-c15079fc52a9" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_c3e06ac4-c59c-452f-a533-acf8521c617b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_c3e06ac4-c59c-452f-a533-acf8521c617b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_c3e06ac4-c59c-452f-a533-acf8521c617b" xlink:to="loc_us-gaap_EquityComponentDomain_c3e06ac4-c59c-452f-a533-acf8521c617b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_c03cc06f-3213-431f-aba6-c1f68802929e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_c3e06ac4-c59c-452f-a533-acf8521c617b" xlink:to="loc_us-gaap_EquityComponentDomain_c03cc06f-3213-431f-aba6-c1f68802929e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_022a1c9d-bf00-42f1-a5c4-639d485284a4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_c03cc06f-3213-431f-aba6-c1f68802929e" xlink:to="loc_us-gaap_CommonStockMember_022a1c9d-bf00-42f1-a5c4-639d485284a4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_97c926c6-433d-46fb-bacd-2adf1da9bd9b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_c03cc06f-3213-431f-aba6-c1f68802929e" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_97c926c6-433d-46fb-bacd-2adf1da9bd9b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_71422d4f-86bf-4422-afe1-67790128b26d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_c03cc06f-3213-431f-aba6-c1f68802929e" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_71422d4f-86bf-4422-afe1-67790128b26d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_c04dc026-1336-484a-baf7-6a4f7860781f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_c03cc06f-3213-431f-aba6-c1f68802929e" xlink:to="loc_us-gaap_RetainedEarningsMember_c04dc026-1336-484a-baf7-6a4f7860781f" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ngmbio.com/role/SummaryofSignificantAccountingPoliciesNarrativeDetails" xlink:type="simple" xlink:href="ngm-20230630.xsd#SummaryofSignificantAccountingPoliciesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.ngmbio.com/role/SummaryofSignificantAccountingPoliciesNarrativeDetails" xlink:type="extended" id="icdca896e91dd475792b4330f8ea6befa_SummaryofSignificantAccountingPoliciesNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_ngm_SummaryOfSignificantAccountingPoliciesLineItems_72ca79a3-c838-48d1-8cef-50ccb48cbdfc" xlink:href="ngm-20230630.xsd#ngm_SummaryOfSignificantAccountingPoliciesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_56e392c8-c34d-473e-bad0-79f02c153e76" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ngm_SummaryOfSignificantAccountingPoliciesLineItems_72ca79a3-c838-48d1-8cef-50ccb48cbdfc" xlink:to="loc_us-gaap_NetIncomeLoss_56e392c8-c34d-473e-bad0-79f02c153e76" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_c8bceeb0-2a56-4e83-8995-dbb2d5c36a0d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ngm_SummaryOfSignificantAccountingPoliciesLineItems_72ca79a3-c838-48d1-8cef-50ccb48cbdfc" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_c8bceeb0-2a56-4e83-8995-dbb2d5c36a0d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsAndShortTermInvestments_3a2f6f1e-f750-4333-83dc-edccfd1a78c2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashCashEquivalentsAndShortTermInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ngm_SummaryOfSignificantAccountingPoliciesLineItems_72ca79a3-c838-48d1-8cef-50ccb48cbdfc" xlink:to="loc_us-gaap_CashCashEquivalentsAndShortTermInvestments_3a2f6f1e-f750-4333-83dc-edccfd1a78c2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_SaleOfStockCommonStockAvailableForIssuance_ce6f1216-cd4f-4dac-8ea6-50b5e9d05e05" xlink:href="ngm-20230630.xsd#ngm_SaleOfStockCommonStockAvailableForIssuance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ngm_SummaryOfSignificantAccountingPoliciesLineItems_72ca79a3-c838-48d1-8cef-50ccb48cbdfc" xlink:to="loc_ngm_SaleOfStockCommonStockAvailableForIssuance_ce6f1216-cd4f-4dac-8ea6-50b5e9d05e05" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_SaleOfStockAggregateOfferingPrice_1686121e-a15d-49bf-858c-96d80481f3f1" xlink:href="ngm-20230630.xsd#ngm_SaleOfStockAggregateOfferingPrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ngm_SummaryOfSignificantAccountingPoliciesLineItems_72ca79a3-c838-48d1-8cef-50ccb48cbdfc" xlink:to="loc_ngm_SaleOfStockAggregateOfferingPrice_1686121e-a15d-49bf-858c-96d80481f3f1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_OtherThanTemporaryImpairmentLossDebtSecuritiesAvailableForSale1_5104c77c-3534-4f15-93d7-5dae75690614" xlink:href="ngm-20230630.xsd#ngm_OtherThanTemporaryImpairmentLossDebtSecuritiesAvailableForSale1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ngm_SummaryOfSignificantAccountingPoliciesLineItems_72ca79a3-c838-48d1-8cef-50ccb48cbdfc" xlink:to="loc_ngm_OtherThanTemporaryImpairmentLossDebtSecuritiesAvailableForSale1_5104c77c-3534-4f15-93d7-5dae75690614" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_ccec1024-15dc-4617-94e0-b1902f3a62e1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ngm_SummaryOfSignificantAccountingPoliciesLineItems_72ca79a3-c838-48d1-8cef-50ccb48cbdfc" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_ccec1024-15dc-4617-94e0-b1902f3a62e1" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfOperatingSegments_6d6ab61e-b363-4113-98a1-f47a3ffa23a5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NumberOfOperatingSegments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ngm_SummaryOfSignificantAccountingPoliciesLineItems_72ca79a3-c838-48d1-8cef-50ccb48cbdfc" xlink:to="loc_us-gaap_NumberOfOperatingSegments_6d6ab61e-b363-4113-98a1-f47a3ffa23a5" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_SummaryOfSignificantAccountingPoliciesTable_7c389625-a9e4-49dd-9ebf-4f2ee3cc3c01" xlink:href="ngm-20230630.xsd#ngm_SummaryOfSignificantAccountingPoliciesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_ngm_SummaryOfSignificantAccountingPoliciesLineItems_72ca79a3-c838-48d1-8cef-50ccb48cbdfc" xlink:to="loc_ngm_SummaryOfSignificantAccountingPoliciesTable_7c389625-a9e4-49dd-9ebf-4f2ee3cc3c01" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MajorCustomersAxis_7c5fff3c-cab1-4ba0-a7ad-d4a3db9fd672" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MajorCustomersAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ngm_SummaryOfSignificantAccountingPoliciesTable_7c389625-a9e4-49dd-9ebf-4f2ee3cc3c01" xlink:to="loc_srt_MajorCustomersAxis_7c5fff3c-cab1-4ba0-a7ad-d4a3db9fd672" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_7c5fff3c-cab1-4ba0-a7ad-d4a3db9fd672_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MajorCustomersAxis_7c5fff3c-cab1-4ba0-a7ad-d4a3db9fd672" xlink:to="loc_srt_NameOfMajorCustomerDomain_7c5fff3c-cab1-4ba0-a7ad-d4a3db9fd672_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_a4e2dc68-c91d-4db6-98f1-563d036575fd" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MajorCustomersAxis_7c5fff3c-cab1-4ba0-a7ad-d4a3db9fd672" xlink:to="loc_srt_NameOfMajorCustomerDomain_a4e2dc68-c91d-4db6-98f1-563d036575fd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_MerckMember_53b05268-d5ac-4320-b00a-715b005d627f" xlink:href="ngm-20230630.xsd#ngm_MerckMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_a4e2dc68-c91d-4db6-98f1-563d036575fd" xlink:to="loc_ngm_MerckMember_53b05268-d5ac-4320-b00a-715b005d627f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_8a21e03f-a1c7-49af-ae0f-19b08e78f7b1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ngm_SummaryOfSignificantAccountingPoliciesTable_7c389625-a9e4-49dd-9ebf-4f2ee3cc3c01" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_8a21e03f-a1c7-49af-ae0f-19b08e78f7b1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_8a21e03f-a1c7-49af-ae0f-19b08e78f7b1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_8a21e03f-a1c7-49af-ae0f-19b08e78f7b1" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_8a21e03f-a1c7-49af-ae0f-19b08e78f7b1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_9cfd17e5-8dd4-47d8-8e5f-63f20e13662b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_8a21e03f-a1c7-49af-ae0f-19b08e78f7b1" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_9cfd17e5-8dd4-47d8-8e5f-63f20e13662b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesRevenueNetMember_f1d0ac4f-b386-4f5b-97ce-363115d332b6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SalesRevenueNetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_9cfd17e5-8dd4-47d8-8e5f-63f20e13662b" xlink:to="loc_us-gaap_SalesRevenueNetMember_f1d0ac4f-b386-4f5b-97ce-363115d332b6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_dc99a681-519e-4e7d-bb97-690e2600882e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ngm_SummaryOfSignificantAccountingPoliciesTable_7c389625-a9e4-49dd-9ebf-4f2ee3cc3c01" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_dc99a681-519e-4e7d-bb97-690e2600882e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_dc99a681-519e-4e7d-bb97-690e2600882e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_dc99a681-519e-4e7d-bb97-690e2600882e" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_dc99a681-519e-4e7d-bb97-690e2600882e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_ccb7ffdf-ac63-4a32-8fde-8a5dc5c5ef92" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_dc99a681-519e-4e7d-bb97-690e2600882e" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_ccb7ffdf-ac63-4a32-8fde-8a5dc5c5ef92" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_ddacf672-d179-45e3-9a71-57b8815e1b64" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CustomerConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_ccb7ffdf-ac63-4a32-8fde-8a5dc5c5ef92" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_ddacf672-d179-45e3-9a71-57b8815e1b64" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ngmbio.com/role/SummaryofSignificantAccountingPoliciesEstimatedUsefulLifeofAssetDetails" xlink:type="simple" xlink:href="ngm-20230630.xsd#SummaryofSignificantAccountingPoliciesEstimatedUsefulLifeofAssetDetails"/>
  <link:definitionLink xlink:role="http://www.ngmbio.com/role/SummaryofSignificantAccountingPoliciesEstimatedUsefulLifeofAssetDetails" xlink:type="extended" id="i275f464fd47f4af48b07e278cfb1a401_SummaryofSignificantAccountingPoliciesEstimatedUsefulLifeofAssetDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_eba08688-6ef5-49f5-a590-e10057d5c6fd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentUsefulLife_00bc1a55-83a6-43ed-9e5c-0073fdb15562" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_eba08688-6ef5-49f5-a590-e10057d5c6fd" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentUsefulLife_00bc1a55-83a6-43ed-9e5c-0073fdb15562" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_1014c2bb-b9da-423f-b9e0-9b97f359d9dd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_eba08688-6ef5-49f5-a590-e10057d5c6fd" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_1014c2bb-b9da-423f-b9e0-9b97f359d9dd" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_3a1276d5-60d3-4dee-ab03-afa7056716a3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_1014c2bb-b9da-423f-b9e0-9b97f359d9dd" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_3a1276d5-60d3-4dee-ab03-afa7056716a3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_3a1276d5-60d3-4dee-ab03-afa7056716a3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_3a1276d5-60d3-4dee-ab03-afa7056716a3" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_3a1276d5-60d3-4dee-ab03-afa7056716a3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_638ea14c-94f7-45e4-9b30-95e63151b43a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_3a1276d5-60d3-4dee-ab03-afa7056716a3" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_638ea14c-94f7-45e4-9b30-95e63151b43a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComputerEquipmentMember_23a7efa9-ea8e-432d-8b45-16f130b8a56c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ComputerEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_638ea14c-94f7-45e4-9b30-95e63151b43a" xlink:to="loc_us-gaap_ComputerEquipmentMember_23a7efa9-ea8e-432d-8b45-16f130b8a56c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_LaboratoryEquipmentAndOfficeFurnitureMember_426f34fe-6e0e-4801-b2be-dac083a9aa72" xlink:href="ngm-20230630.xsd#ngm_LaboratoryEquipmentAndOfficeFurnitureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_638ea14c-94f7-45e4-9b30-95e63151b43a" xlink:to="loc_ngm_LaboratoryEquipmentAndOfficeFurnitureMember_426f34fe-6e0e-4801-b2be-dac083a9aa72" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ngmbio.com/role/SummaryofSignificantAccountingPoliciesPotentiallyDilutiveSecuritiesNotIncludedintheDilutedNetLossPerShareCalculationsDetails" xlink:type="simple" xlink:href="ngm-20230630.xsd#SummaryofSignificantAccountingPoliciesPotentiallyDilutiveSecuritiesNotIncludedintheDilutedNetLossPerShareCalculationsDetails"/>
  <link:definitionLink xlink:role="http://www.ngmbio.com/role/SummaryofSignificantAccountingPoliciesPotentiallyDilutiveSecuritiesNotIncludedintheDilutedNetLossPerShareCalculationsDetails" xlink:type="extended" id="i08374d8c5f184a3d96b9e332b2198d24_SummaryofSignificantAccountingPoliciesPotentiallyDilutiveSecuritiesNotIncludedintheDilutedNetLossPerShareCalculationsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_1d982e94-8795-4574-9adf-099bb0605fdd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_fa0b4199-e164-4f8e-abdb-7ef6d7a1a93b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_1d982e94-8795-4574-9adf-099bb0605fdd" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_fa0b4199-e164-4f8e-abdb-7ef6d7a1a93b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_eb134d63-e7d3-4d8d-b081-8f560f584a03" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_1d982e94-8795-4574-9adf-099bb0605fdd" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_eb134d63-e7d3-4d8d-b081-8f560f584a03" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_aa86d86a-1644-4b39-ba4e-9c38429288d7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_eb134d63-e7d3-4d8d-b081-8f560f584a03" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_aa86d86a-1644-4b39-ba4e-9c38429288d7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_aa86d86a-1644-4b39-ba4e-9c38429288d7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_aa86d86a-1644-4b39-ba4e-9c38429288d7" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_aa86d86a-1644-4b39-ba4e-9c38429288d7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_61128dd6-9ace-4a61-b8cc-61f1813c6834" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_aa86d86a-1644-4b39-ba4e-9c38429288d7" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_61128dd6-9ace-4a61-b8cc-61f1813c6834" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_OptionsToPurchaseCommonStockMember_19769ea1-e557-4b83-9718-ca936638efe6" xlink:href="ngm-20230630.xsd#ngm_OptionsToPurchaseCommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_61128dd6-9ace-4a61-b8cc-61f1813c6834" xlink:to="loc_ngm_OptionsToPurchaseCommonStockMember_19769ea1-e557-4b83-9718-ca936638efe6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockMember_37c1c29c-880b-430d-8d7d-498a3d653574" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_61128dd6-9ace-4a61-b8cc-61f1813c6834" xlink:to="loc_us-gaap_EmployeeStockMember_37c1c29c-880b-430d-8d7d-498a3d653574" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_67367837-d1d2-4d7a-913a-dd315fda82e6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_61128dd6-9ace-4a61-b8cc-61f1813c6834" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_67367837-d1d2-4d7a-913a-dd315fda82e6" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ngmbio.com/role/FairValueMeasurementsScheduleofCashandCashEquivalentsandMarketableSecuritiesClassifiedasAvailableforsaleSecuritiesDetails" xlink:type="simple" xlink:href="ngm-20230630.xsd#FairValueMeasurementsScheduleofCashandCashEquivalentsandMarketableSecuritiesClassifiedasAvailableforsaleSecuritiesDetails"/>
  <link:definitionLink xlink:role="http://www.ngmbio.com/role/FairValueMeasurementsScheduleofCashandCashEquivalentsandMarketableSecuritiesClassifiedasAvailableforsaleSecuritiesDetails" xlink:type="extended" id="i0b8e5cfefe68480bb7e5059e0c6c7692_FairValueMeasurementsScheduleofCashandCashEquivalentsandMarketableSecuritiesClassifiedasAvailableforsaleSecuritiesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_92de2fec-a6c4-42bb-81cf-cdb097d93bad" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_763fc274-0ffc-45df-9261-f0e4f3b3ceef" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_92de2fec-a6c4-42bb-81cf-cdb097d93bad" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_763fc274-0ffc-45df-9261-f0e4f3b3ceef" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_6b611216-abef-44fc-b15e-21b633695690" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_92de2fec-a6c4-42bb-81cf-cdb097d93bad" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_6b611216-abef-44fc-b15e-21b633695690" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_6f5926c8-2d72-4c00-9712-dfe578316054" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_92de2fec-a6c4-42bb-81cf-cdb097d93bad" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_6f5926c8-2d72-4c00-9712-dfe578316054" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_4f350985-519f-4a4f-8ae7-d911fe75c70f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_92de2fec-a6c4-42bb-81cf-cdb097d93bad" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_4f350985-519f-4a4f-8ae7-d911fe75c70f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_ca38c6dc-779a-46ef-a608-e0662db96931" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtSecuritiesAvailableForSaleTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_92de2fec-a6c4-42bb-81cf-cdb097d93bad" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_ca38c6dc-779a-46ef-a608-e0662db96931" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_3ba7a597-2381-41a5-92e8-da0f2c955ae3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_ca38c6dc-779a-46ef-a608-e0662db96931" xlink:to="loc_us-gaap_FinancialInstrumentAxis_3ba7a597-2381-41a5-92e8-da0f2c955ae3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_3ba7a597-2381-41a5-92e8-da0f2c955ae3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_3ba7a597-2381-41a5-92e8-da0f2c955ae3" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_3ba7a597-2381-41a5-92e8-da0f2c955ae3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_13fe4efb-a9e3-4a65-b3a1-2bd1cf98b5ed" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_3ba7a597-2381-41a5-92e8-da0f2c955ae3" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_13fe4efb-a9e3-4a65-b3a1-2bd1cf98b5ed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_257d77f7-e565-4af8-882d-d3e38467a00b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_USTreasurySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_13fe4efb-a9e3-4a65-b3a1-2bd1cf98b5ed" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_257d77f7-e565-4af8-882d-d3e38467a00b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MoneyMarketFundsMember_2e7b3d54-36fb-49f1-b954-611766bc5ab4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MoneyMarketFundsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_13fe4efb-a9e3-4a65-b3a1-2bd1cf98b5ed" xlink:to="loc_us-gaap_MoneyMarketFundsMember_2e7b3d54-36fb-49f1-b954-611766bc5ab4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialPaperMember_98ea5b4c-d894-438d-8cd0-ca18f9ecc5ca" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommercialPaperMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_13fe4efb-a9e3-4a65-b3a1-2bd1cf98b5ed" xlink:to="loc_us-gaap_CommercialPaperMember_98ea5b4c-d894-438d-8cd0-ca18f9ecc5ca" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_1beb2d58-bdbf-4260-bf65-4f7a3408471f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_USGovernmentAgenciesDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_13fe4efb-a9e3-4a65-b3a1-2bd1cf98b5ed" xlink:to="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_1beb2d58-bdbf-4260-bf65-4f7a3408471f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateBondSecuritiesMember_9b9b7774-29d7-4146-932a-dbb029bcde0c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CorporateBondSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_13fe4efb-a9e3-4a65-b3a1-2bd1cf98b5ed" xlink:to="loc_us-gaap_CorporateBondSecuritiesMember_9b9b7774-29d7-4146-932a-dbb029bcde0c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_9998bb2a-30e0-49e3-b5da-b50f0b5d8e69" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BalanceSheetLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_ca38c6dc-779a-46ef-a608-e0662db96931" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_9998bb2a-30e0-49e3-b5da-b50f0b5d8e69" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_9998bb2a-30e0-49e3-b5da-b50f0b5d8e69_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_9998bb2a-30e0-49e3-b5da-b50f0b5d8e69" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_9998bb2a-30e0-49e3-b5da-b50f0b5d8e69_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_e315a4af-3d72-4cc7-805d-4dff1d92e754" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_9998bb2a-30e0-49e3-b5da-b50f0b5d8e69" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_e315a4af-3d72-4cc7-805d-4dff1d92e754" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsMember_ff1f36a6-a629-42e7-b6f2-de0d5878a127" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_e315a4af-3d72-4cc7-805d-4dff1d92e754" xlink:to="loc_us-gaap_CashAndCashEquivalentsMember_ff1f36a6-a629-42e7-b6f2-de0d5878a127" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermInvestmentsMember_22a41cb8-c84e-4c5a-8741-c2e61e5a75af" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShortTermInvestmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_e315a4af-3d72-4cc7-805d-4dff1d92e754" xlink:to="loc_us-gaap_ShortTermInvestmentsMember_22a41cb8-c84e-4c5a-8741-c2e61e5a75af" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ngmbio.com/role/FairValueMeasurementsScheduleofAssetsandLiabilitiesMeasuredatFairValueonRecurringBasisDetails" xlink:type="simple" xlink:href="ngm-20230630.xsd#FairValueMeasurementsScheduleofAssetsandLiabilitiesMeasuredatFairValueonRecurringBasisDetails"/>
  <link:definitionLink xlink:role="http://www.ngmbio.com/role/FairValueMeasurementsScheduleofAssetsandLiabilitiesMeasuredatFairValueonRecurringBasisDetails" xlink:type="extended" id="ia3f0c14121a54ed7af45609714f67dea_FairValueMeasurementsScheduleofAssetsandLiabilitiesMeasuredatFairValueonRecurringBasisDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_6cd23cf4-eb2b-468d-8398-f370cbb20149" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosureAbstract_41848c2b-ffa7-4657-a1bf-0f04eb5ce216" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsFairValueDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_6cd23cf4-eb2b-468d-8398-f370cbb20149" xlink:to="loc_us-gaap_AssetsFairValueDisclosureAbstract_41848c2b-ffa7-4657-a1bf-0f04eb5ce216" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_a729c2b4-d2b6-4865-8c2d-92747b6fccdf" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_41848c2b-ffa7-4657-a1bf-0f04eb5ce216" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_a729c2b4-d2b6-4865-8c2d-92747b6fccdf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_4723dcab-ac82-475f-8eca-75a7dd9e8e2b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_6cd23cf4-eb2b-468d-8398-f370cbb20149" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_4723dcab-ac82-475f-8eca-75a7dd9e8e2b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_c47608c9-222f-4c1d-9b93-133729135ef6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_4723dcab-ac82-475f-8eca-75a7dd9e8e2b" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_c47608c9-222f-4c1d-9b93-133729135ef6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_c47608c9-222f-4c1d-9b93-133729135ef6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_c47608c9-222f-4c1d-9b93-133729135ef6" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_c47608c9-222f-4c1d-9b93-133729135ef6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_411d483c-a5e5-40a4-a69a-8f6db447ab4f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_c47608c9-222f-4c1d-9b93-133729135ef6" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_411d483c-a5e5-40a4-a69a-8f6db447ab4f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_a7aee748-b31e-4aa9-b397-c2e52613b9a2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsRecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_411d483c-a5e5-40a4-a69a-8f6db447ab4f" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_a7aee748-b31e-4aa9-b397-c2e52613b9a2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByAssetClassAxis_45e3516e-d9de-4e46-835b-e29e096c60f4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByAssetClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_4723dcab-ac82-475f-8eca-75a7dd9e8e2b" xlink:to="loc_us-gaap_FairValueByAssetClassAxis_45e3516e-d9de-4e46-835b-e29e096c60f4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_45e3516e-d9de-4e46-835b-e29e096c60f4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_45e3516e-d9de-4e46-835b-e29e096c60f4" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_45e3516e-d9de-4e46-835b-e29e096c60f4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_f4d6bc31-40de-4d99-abd8-6c3a7bc84ff4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_45e3516e-d9de-4e46-835b-e29e096c60f4" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_f4d6bc31-40de-4d99-abd8-6c3a7bc84ff4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_d600e72e-2214-4760-ab6e-df42e576ec63" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_USTreasurySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_f4d6bc31-40de-4d99-abd8-6c3a7bc84ff4" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_d600e72e-2214-4760-ab6e-df42e576ec63" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MoneyMarketFundsMember_821b7295-38ee-4bfc-b4a0-5fd498268ae3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MoneyMarketFundsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_f4d6bc31-40de-4d99-abd8-6c3a7bc84ff4" xlink:to="loc_us-gaap_MoneyMarketFundsMember_821b7295-38ee-4bfc-b4a0-5fd498268ae3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialPaperMember_a74a9afd-892a-48b0-81f5-d8646fd3ccde" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommercialPaperMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_f4d6bc31-40de-4d99-abd8-6c3a7bc84ff4" xlink:to="loc_us-gaap_CommercialPaperMember_a74a9afd-892a-48b0-81f5-d8646fd3ccde" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_cc1d2be5-0412-4867-8f04-cb6d9dd39300" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_USGovernmentAgenciesDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_f4d6bc31-40de-4d99-abd8-6c3a7bc84ff4" xlink:to="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_cc1d2be5-0412-4867-8f04-cb6d9dd39300" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateBondSecuritiesMember_73de1a96-9aed-4a2d-85c7-6a7124a7ae80" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CorporateBondSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_f4d6bc31-40de-4d99-abd8-6c3a7bc84ff4" xlink:to="loc_us-gaap_CorporateBondSecuritiesMember_73de1a96-9aed-4a2d-85c7-6a7124a7ae80" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_31874467-cea4-4b8e-8b50-179140fc5658" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_4723dcab-ac82-475f-8eca-75a7dd9e8e2b" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_31874467-cea4-4b8e-8b50-179140fc5658" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_31874467-cea4-4b8e-8b50-179140fc5658_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_31874467-cea4-4b8e-8b50-179140fc5658" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_31874467-cea4-4b8e-8b50-179140fc5658_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_c157d054-d63c-4289-887c-5669276fc3d1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_31874467-cea4-4b8e-8b50-179140fc5658" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_c157d054-d63c-4289-887c-5669276fc3d1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_cd640e71-51ff-44d7-8d11-d0ab52bb8a3e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_c157d054-d63c-4289-887c-5669276fc3d1" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_cd640e71-51ff-44d7-8d11-d0ab52bb8a3e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_8a265558-e531-4e86-aa68-2ffe6231cce6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_c157d054-d63c-4289-887c-5669276fc3d1" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_8a265558-e531-4e86-aa68-2ffe6231cce6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_1c33886a-9dc1-42f8-ae5a-0016a8da79af" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_c157d054-d63c-4289-887c-5669276fc3d1" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_1c33886a-9dc1-42f8-ae5a-0016a8da79af" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ngmbio.com/role/BalanceSheetComponentsScheduleofPropertyandEquipmentDetails" xlink:type="simple" xlink:href="ngm-20230630.xsd#BalanceSheetComponentsScheduleofPropertyandEquipmentDetails"/>
  <link:definitionLink xlink:role="http://www.ngmbio.com/role/BalanceSheetComponentsScheduleofPropertyandEquipmentDetails" xlink:type="extended" id="i4ab0508c9d6845199d1aca3b542ad3b5_BalanceSheetComponentsScheduleofPropertyandEquipmentDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_a31d6b68-aa8d-4cf7-b613-87011ec9683e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_c65d2d3e-9eb1-47ae-92f5-707f56dbede7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_a31d6b68-aa8d-4cf7-b613-87011ec9683e" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_c65d2d3e-9eb1-47ae-92f5-707f56dbede7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_288acfde-c274-410f-aba0-f1a4252a4972" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_a31d6b68-aa8d-4cf7-b613-87011ec9683e" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_288acfde-c274-410f-aba0-f1a4252a4972" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_a1b3a23c-5e67-47e4-9236-1ca1f88486f1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_a31d6b68-aa8d-4cf7-b613-87011ec9683e" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_a1b3a23c-5e67-47e4-9236-1ca1f88486f1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_51d7156e-a69f-49d8-a1c2-9a08e11728ff" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_a31d6b68-aa8d-4cf7-b613-87011ec9683e" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_51d7156e-a69f-49d8-a1c2-9a08e11728ff" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_38a2ad77-1e09-4efc-9282-57095207cb3c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_51d7156e-a69f-49d8-a1c2-9a08e11728ff" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_38a2ad77-1e09-4efc-9282-57095207cb3c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_38a2ad77-1e09-4efc-9282-57095207cb3c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_38a2ad77-1e09-4efc-9282-57095207cb3c" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_38a2ad77-1e09-4efc-9282-57095207cb3c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_2f915224-3662-4bf4-9e8a-ce782377e0df" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_38a2ad77-1e09-4efc-9282-57095207cb3c" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_2f915224-3662-4bf4-9e8a-ce782377e0df" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeaseholdImprovementsMember_e8acf8f5-6449-4744-aa5d-29496202806b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LeaseholdImprovementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_2f915224-3662-4bf4-9e8a-ce782377e0df" xlink:to="loc_us-gaap_LeaseholdImprovementsMember_e8acf8f5-6449-4744-aa5d-29496202806b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_LaboratoryEquipmentAndOfficeFurnitureMember_341a909b-0326-4ab2-932b-2282165d2f40" xlink:href="ngm-20230630.xsd#ngm_LaboratoryEquipmentAndOfficeFurnitureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_2f915224-3662-4bf4-9e8a-ce782377e0df" xlink:to="loc_ngm_LaboratoryEquipmentAndOfficeFurnitureMember_341a909b-0326-4ab2-932b-2282165d2f40" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComputerEquipmentMember_c2374164-396c-48ee-98ff-07589322a4bc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ComputerEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_2f915224-3662-4bf4-9e8a-ce782377e0df" xlink:to="loc_us-gaap_ComputerEquipmentMember_c2374164-396c-48ee-98ff-07589322a4bc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConstructionInProgressMember_86f87eec-db49-44c4-a977-06162e0b730e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConstructionInProgressMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_2f915224-3662-4bf4-9e8a-ce782377e0df" xlink:to="loc_us-gaap_ConstructionInProgressMember_86f87eec-db49-44c4-a977-06162e0b730e" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ngmbio.com/role/ResearchCollaborationandLicenseAgreementsNarrativeDetails" xlink:type="simple" xlink:href="ngm-20230630.xsd#ResearchCollaborationandLicenseAgreementsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.ngmbio.com/role/ResearchCollaborationandLicenseAgreementsNarrativeDetails" xlink:type="extended" id="ifba31a23f17147488487d291fb506f32_ResearchCollaborationandLicenseAgreementsNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_d0491659-0767-48fc-a56c-d49e231635e3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_ResearchAndDevelopmentServicePerformancePeriod_7bcdbb7b-e647-47fa-b00e-ca0cba2b1537" xlink:href="ngm-20230630.xsd#ngm_ResearchAndDevelopmentServicePerformancePeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_d0491659-0767-48fc-a56c-d49e231635e3" xlink:to="loc_ngm_ResearchAndDevelopmentServicePerformancePeriod_7bcdbb7b-e647-47fa-b00e-ca0cba2b1537" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_ResearchAndDevelopmentOptionExtendTerm_cba2ed3c-6189-4ff3-83f3-8cabc1b8257b" xlink:href="ngm-20230630.xsd#ngm_ResearchAndDevelopmentOptionExtendTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_d0491659-0767-48fc-a56c-d49e231635e3" xlink:to="loc_ngm_ResearchAndDevelopmentOptionExtendTerm_cba2ed3c-6189-4ff3-83f3-8cabc1b8257b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_AmountOfFundReceivedForResearchActivities_57caf857-d501-4898-8a38-9d95c5faa562" xlink:href="ngm-20230630.xsd#ngm_AmountOfFundReceivedForResearchActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_d0491659-0767-48fc-a56c-d49e231635e3" xlink:to="loc_ngm_AmountOfFundReceivedForResearchActivities_57caf857-d501-4898-8a38-9d95c5faa562" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_ResearchCollaborationAndLicenseAgreementsExtensionFee_17165db9-f628-43ba-82ea-c0022caccf41" xlink:href="ngm-20230630.xsd#ngm_ResearchCollaborationAndLicenseAgreementsExtensionFee"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_d0491659-0767-48fc-a56c-d49e231635e3" xlink:to="loc_ngm_ResearchCollaborationAndLicenseAgreementsExtensionFee_17165db9-f628-43ba-82ea-c0022caccf41" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_AmountOfAdditionalFundReceivedForResearchActivities_e44988ff-82df-4acb-8ae1-c926adb103dd" xlink:href="ngm-20230630.xsd#ngm_AmountOfAdditionalFundReceivedForResearchActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_d0491659-0767-48fc-a56c-d49e231635e3" xlink:to="loc_ngm_AmountOfAdditionalFundReceivedForResearchActivities_e44988ff-82df-4acb-8ae1-c926adb103dd" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_ResearchAndDevelopmentOptionExerciseFee_de11ed33-ee06-4726-a012-fefc9bad1ed0" xlink:href="ngm-20230630.xsd#ngm_ResearchAndDevelopmentOptionExerciseFee"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_d0491659-0767-48fc-a56c-d49e231635e3" xlink:to="loc_ngm_ResearchAndDevelopmentOptionExerciseFee_de11ed33-ee06-4726-a012-fefc9bad1ed0" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_MilestonePaymentForPotentialAchievementOfCertainClinicalDevelopmentEvents_4d536fad-8f7e-4965-ae8e-e6bc03a9e34b" xlink:href="ngm-20230630.xsd#ngm_MilestonePaymentForPotentialAchievementOfCertainClinicalDevelopmentEvents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_d0491659-0767-48fc-a56c-d49e231635e3" xlink:to="loc_ngm_MilestonePaymentForPotentialAchievementOfCertainClinicalDevelopmentEvents_4d536fad-8f7e-4965-ae8e-e6bc03a9e34b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_ResearchAndDevelopmentOptionRemainingExtensionTerm_fa97254a-f4f2-410a-91a8-2c5a83c20f81" xlink:href="ngm-20230630.xsd#ngm_ResearchAndDevelopmentOptionRemainingExtensionTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_d0491659-0767-48fc-a56c-d49e231635e3" xlink:to="loc_ngm_ResearchAndDevelopmentOptionRemainingExtensionTerm_fa97254a-f4f2-410a-91a8-2c5a83c20f81" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_ResearchAndDevelopmentPerformanceObligationPeriod_6ed18337-b94d-4e21-983f-7eef19ab8e5b" xlink:href="ngm-20230630.xsd#ngm_ResearchAndDevelopmentPerformanceObligationPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_d0491659-0767-48fc-a56c-d49e231635e3" xlink:to="loc_ngm_ResearchAndDevelopmentPerformanceObligationPeriod_6ed18337-b94d-4e21-983f-7eef19ab8e5b" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_0d4df4a3-1eb9-4811-9f60-45d7122f5e54" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_d0491659-0767-48fc-a56c-d49e231635e3" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_0d4df4a3-1eb9-4811-9f60-45d7122f5e54" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_ResearchAndDevelopmentReimbursableExpense_23a80368-2ccf-4ef4-a511-7e50377d9a03" xlink:href="ngm-20230630.xsd#ngm_ResearchAndDevelopmentReimbursableExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_d0491659-0767-48fc-a56c-d49e231635e3" xlink:to="loc_ngm_ResearchAndDevelopmentReimbursableExpense_23a80368-2ccf-4ef4-a511-7e50377d9a03" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNet_c0893449-d580-4b96-b5e1-31ea460d08ba" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccountsReceivableNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_d0491659-0767-48fc-a56c-d49e231635e3" xlink:to="loc_us-gaap_AccountsReceivableNet_c0893449-d580-4b96-b5e1-31ea460d08ba" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_AmountOfFundsExpectedToBeReceivedForResearchActivities_4c6362fb-e558-4b24-949b-884a23e9a7b6" xlink:href="ngm-20230630.xsd#ngm_AmountOfFundsExpectedToBeReceivedForResearchActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_d0491659-0767-48fc-a56c-d49e231635e3" xlink:to="loc_ngm_AmountOfFundsExpectedToBeReceivedForResearchActivities_4c6362fb-e558-4b24-949b-884a23e9a7b6" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_CollaborativeArrangementPercentOfStockOwnedByCounterparty_693f6e5f-e7bc-4162-88f7-e335806c2076" xlink:href="ngm-20230630.xsd#ngm_CollaborativeArrangementPercentOfStockOwnedByCounterparty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_d0491659-0767-48fc-a56c-d49e231635e3" xlink:to="loc_ngm_CollaborativeArrangementPercentOfStockOwnedByCounterparty_693f6e5f-e7bc-4162-88f7-e335806c2076" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerAssetNetCurrent_0317c6d3-28dc-4be5-8eda-4b0dd371f615" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ContractWithCustomerAssetNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_d0491659-0767-48fc-a56c-d49e231635e3" xlink:to="loc_us-gaap_ContractWithCustomerAssetNetCurrent_0317c6d3-28dc-4be5-8eda-4b0dd371f615" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityCurrent_03bcd51e-ce96-4d5a-9ad7-1c96a28bb2fb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ContractWithCustomerLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_d0491659-0767-48fc-a56c-d49e231635e3" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityCurrent_03bcd51e-ce96-4d5a-9ad7-1c96a28bb2fb" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_9a0ebd04-3faa-4516-913a-6b6a01b1fad9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_d0491659-0767-48fc-a56c-d49e231635e3" xlink:to="loc_us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_9a0ebd04-3faa-4516-913a-6b6a01b1fad9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_d1eb5de0-0e18-4407-bd7e-ea63c07854c1" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_9a0ebd04-3faa-4516-913a-6b6a01b1fad9" xlink:to="loc_srt_CounterpartyNameAxis_d1eb5de0-0e18-4407-bd7e-ea63c07854c1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_d1eb5de0-0e18-4407-bd7e-ea63c07854c1_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_d1eb5de0-0e18-4407-bd7e-ea63c07854c1" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_d1eb5de0-0e18-4407-bd7e-ea63c07854c1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_095c922f-5772-4948-8e02-d2b45f69e034" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_d1eb5de0-0e18-4407-bd7e-ea63c07854c1" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_095c922f-5772-4948-8e02-d2b45f69e034" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_MerckSharpAndDohmeCorporationMember_a0ea65ac-864b-410e-a6f1-8e2d5882dec5" xlink:href="ngm-20230630.xsd#ngm_MerckSharpAndDohmeCorporationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_095c922f-5772-4948-8e02-d2b45f69e034" xlink:to="loc_ngm_MerckSharpAndDohmeCorporationMember_a0ea65ac-864b-410e-a6f1-8e2d5882dec5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfArrangementAxis_b33aabf2-bd5c-48fb-a9e7-4513718bd945" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TypeOfArrangementAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_9a0ebd04-3faa-4516-913a-6b6a01b1fad9" xlink:to="loc_us-gaap_TypeOfArrangementAxis_b33aabf2-bd5c-48fb-a9e7-4513718bd945" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_b33aabf2-bd5c-48fb-a9e7-4513718bd945_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ArrangementsAndNonarrangementTransactionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_TypeOfArrangementAxis_b33aabf2-bd5c-48fb-a9e7-4513718bd945" xlink:to="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_b33aabf2-bd5c-48fb-a9e7-4513718bd945_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_e7c27187-8c65-4744-9a58-94e8c3b1b78a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ArrangementsAndNonarrangementTransactionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_TypeOfArrangementAxis_b33aabf2-bd5c-48fb-a9e7-4513718bd945" xlink:to="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_e7c27187-8c65-4744-9a58-94e8c3b1b78a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_MerckOriginalAgreementMember_27dcf3ec-e3a6-4df6-a0fe-5f6f01022d08" xlink:href="ngm-20230630.xsd#ngm_MerckOriginalAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_e7c27187-8c65-4744-9a58-94e8c3b1b78a" xlink:to="loc_ngm_MerckOriginalAgreementMember_27dcf3ec-e3a6-4df6-a0fe-5f6f01022d08" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_MerckAmendedAgreementMember_e6d83054-a90d-48d2-b072-45ebbc1c5972" xlink:href="ngm-20230630.xsd#ngm_MerckAmendedAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_e7c27187-8c65-4744-9a58-94e8c3b1b78a" xlink:to="loc_ngm_MerckAmendedAgreementMember_e6d83054-a90d-48d2-b072-45ebbc1c5972" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_ClinicalDevelopmentEventAxis_5008f00f-8742-44cc-9d09-7250fc37aa6a" xlink:href="ngm-20230630.xsd#ngm_ClinicalDevelopmentEventAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_9a0ebd04-3faa-4516-913a-6b6a01b1fad9" xlink:to="loc_ngm_ClinicalDevelopmentEventAxis_5008f00f-8742-44cc-9d09-7250fc37aa6a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_ClinicalDevelopmentEventDomain_5008f00f-8742-44cc-9d09-7250fc37aa6a_default" xlink:href="ngm-20230630.xsd#ngm_ClinicalDevelopmentEventDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_ngm_ClinicalDevelopmentEventAxis_5008f00f-8742-44cc-9d09-7250fc37aa6a" xlink:to="loc_ngm_ClinicalDevelopmentEventDomain_5008f00f-8742-44cc-9d09-7250fc37aa6a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_ClinicalDevelopmentEventDomain_58151a75-c72c-4331-9feb-4b069d076121" xlink:href="ngm-20230630.xsd#ngm_ClinicalDevelopmentEventDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_ngm_ClinicalDevelopmentEventAxis_5008f00f-8742-44cc-9d09-7250fc37aa6a" xlink:to="loc_ngm_ClinicalDevelopmentEventDomain_58151a75-c72c-4331-9feb-4b069d076121" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_ProofOfConceptTrialCVMResearchProgramMember_ea3d8a43-50d6-4067-8093-f5870b99402a" xlink:href="ngm-20230630.xsd#ngm_ProofOfConceptTrialCVMResearchProgramMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ngm_ClinicalDevelopmentEventDomain_58151a75-c72c-4331-9feb-4b069d076121" xlink:to="loc_ngm_ProofOfConceptTrialCVMResearchProgramMember_ea3d8a43-50d6-4067-8093-f5870b99402a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementScenarioAxis_aaf760c1-879f-450e-9902-d44c6f653d0a" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_StatementScenarioAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_9a0ebd04-3faa-4516-913a-6b6a01b1fad9" xlink:to="loc_srt_StatementScenarioAxis_aaf760c1-879f-450e-9902-d44c6f653d0a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_aaf760c1-879f-450e-9902-d44c6f653d0a_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementScenarioAxis_aaf760c1-879f-450e-9902-d44c6f653d0a" xlink:to="loc_srt_ScenarioUnspecifiedDomain_aaf760c1-879f-450e-9902-d44c6f653d0a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_c4f51565-ac86-4cbd-b6bb-5d578842751e" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementScenarioAxis_aaf760c1-879f-450e-9902-d44c6f653d0a" xlink:to="loc_srt_ScenarioUnspecifiedDomain_c4f51565-ac86-4cbd-b6bb-5d578842751e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioForecastMember_9927b6a0-3d12-4e9a-848f-a330d69613af" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ScenarioForecastMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ScenarioUnspecifiedDomain_c4f51565-ac86-4cbd-b6bb-5d578842751e" xlink:to="loc_srt_ScenarioForecastMember_9927b6a0-3d12-4e9a-848f-a330d69613af" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionAxis_4fd63785-68c7-49d4-958d-3a83fb3a4431" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_9a0ebd04-3faa-4516-913a-6b6a01b1fad9" xlink:to="loc_us-gaap_RelatedPartyTransactionAxis_4fd63785-68c7-49d4-958d-3a83fb3a4431" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_4fd63785-68c7-49d4-958d-3a83fb3a4431_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_4fd63785-68c7-49d4-958d-3a83fb3a4431" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_4fd63785-68c7-49d4-958d-3a83fb3a4431_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_b7185e3b-1b25-4460-b53f-35831fd288a2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_4fd63785-68c7-49d4-958d-3a83fb3a4431" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_b7185e3b-1b25-4460-b53f-35831fd288a2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_ResearchCollaborationAndLicenseAgreementsMember_6bf28205-decc-4f95-b908-8f3ca00e3e4b" xlink:href="ngm-20230630.xsd#ngm_ResearchCollaborationAndLicenseAgreementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_b7185e3b-1b25-4460-b53f-35831fd288a2" xlink:to="loc_ngm_ResearchCollaborationAndLicenseAgreementsMember_6bf28205-decc-4f95-b908-8f3ca00e3e4b" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ngmbio.com/role/ResearchCollaborationandLicenseAgreementsScheduleofRecognizedRevenuefromCollaborationandLicenseAgreementsDetails" xlink:type="simple" xlink:href="ngm-20230630.xsd#ResearchCollaborationandLicenseAgreementsScheduleofRecognizedRevenuefromCollaborationandLicenseAgreementsDetails"/>
  <link:definitionLink xlink:role="http://www.ngmbio.com/role/ResearchCollaborationandLicenseAgreementsScheduleofRecognizedRevenuefromCollaborationandLicenseAgreementsDetails" xlink:type="extended" id="i85bbe98734324a85be8b229f3cf704fc_ResearchCollaborationandLicenseAgreementsScheduleofRecognizedRevenuefromCollaborationandLicenseAgreementsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_6dbd8e67-a97d-445e-b562-28634cece971" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_d67c119a-c983-4399-9ca6-c0a763e0f85a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_6dbd8e67-a97d-445e-b562-28634cece971" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_d67c119a-c983-4399-9ca6-c0a763e0f85a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_a5d82203-11d3-4e62-8e39-4c4da1e0311b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_6dbd8e67-a97d-445e-b562-28634cece971" xlink:to="loc_us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_a5d82203-11d3-4e62-8e39-4c4da1e0311b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfArrangementAxis_c79122b1-4ac2-4f79-b2d3-9ad653b9df9a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TypeOfArrangementAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_a5d82203-11d3-4e62-8e39-4c4da1e0311b" xlink:to="loc_us-gaap_TypeOfArrangementAxis_c79122b1-4ac2-4f79-b2d3-9ad653b9df9a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_c79122b1-4ac2-4f79-b2d3-9ad653b9df9a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ArrangementsAndNonarrangementTransactionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_TypeOfArrangementAxis_c79122b1-4ac2-4f79-b2d3-9ad653b9df9a" xlink:to="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_c79122b1-4ac2-4f79-b2d3-9ad653b9df9a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_bc1420be-f894-4619-a506-e2b6abe207b4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ArrangementsAndNonarrangementTransactionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_TypeOfArrangementAxis_c79122b1-4ac2-4f79-b2d3-9ad653b9df9a" xlink:to="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_bc1420be-f894-4619-a506-e2b6abe207b4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CollaborativeArrangementMember_4a334224-06c3-4196-8ce8-69449320ae96" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CollaborativeArrangementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_bc1420be-f894-4619-a506-e2b6abe207b4" xlink:to="loc_us-gaap_CollaborativeArrangementMember_4a334224-06c3-4196-8ce8-69449320ae96" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionAxis_f4fd0587-512a-40a9-9b8a-e390b0c339f8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_a5d82203-11d3-4e62-8e39-4c4da1e0311b" xlink:to="loc_us-gaap_RelatedPartyTransactionAxis_f4fd0587-512a-40a9-9b8a-e390b0c339f8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_f4fd0587-512a-40a9-9b8a-e390b0c339f8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_f4fd0587-512a-40a9-9b8a-e390b0c339f8" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_f4fd0587-512a-40a9-9b8a-e390b0c339f8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_a677bbd5-3b04-481b-995e-24df7908225c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_f4fd0587-512a-40a9-9b8a-e390b0c339f8" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_a677bbd5-3b04-481b-995e-24df7908225c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_MerckSharpAndDohmeCorporationMember_ca727957-8b1f-43eb-87f2-e6cc5b1aab0f" xlink:href="ngm-20230630.xsd#ngm_MerckSharpAndDohmeCorporationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_a677bbd5-3b04-481b-995e-24df7908225c" xlink:to="loc_ngm_MerckSharpAndDohmeCorporationMember_ca727957-8b1f-43eb-87f2-e6cc5b1aab0f" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ngmbio.com/role/CommitmentsandContingenciesNarrativeDetails" xlink:type="simple" xlink:href="ngm-20230630.xsd#CommitmentsandContingenciesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.ngmbio.com/role/CommitmentsandContingenciesNarrativeDetails" xlink:type="extended" id="i86ed2cb40cd048af9cf613cedb8b6ad6_CommitmentsandContingenciesNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeasedAssetsLineItems_6013593f-5730-4e29-939e-f16060341492" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingLeasedAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AreaOfRealEstateProperty_d90961c6-043e-4832-9855-0b3e1383cc6a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AreaOfRealEstateProperty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_6013593f-5730-4e29-939e-f16060341492" xlink:to="loc_us-gaap_AreaOfRealEstateProperty_d90961c6-043e-4832-9855-0b3e1383cc6a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TenantImprovements_2d97b543-a750-406c-80a5-81f8fef62b6f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TenantImprovements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_6013593f-5730-4e29-939e-f16060341492" xlink:to="loc_us-gaap_TenantImprovements_2d97b543-a750-406c-80a5-81f8fef62b6f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_959b1dba-6259-4346-901d-008259df3119" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_6013593f-5730-4e29-939e-f16060341492" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_959b1dba-6259-4346-901d-008259df3119" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseTermOfContract_8c18fecb-cabc-422f-a130-14f5fc9fd117" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LesseeOperatingLeaseTermOfContract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_6013593f-5730-4e29-939e-f16060341492" xlink:to="loc_us-gaap_LesseeOperatingLeaseTermOfContract_8c18fecb-cabc-422f-a130-14f5fc9fd117" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecurityDeposit_92a02b54-ff50-4e1a-80bb-3e66cd4ce2ef" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecurityDeposit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_6013593f-5730-4e29-939e-f16060341492" xlink:to="loc_us-gaap_SecurityDeposit_92a02b54-ff50-4e1a-80bb-3e66cd4ce2ef" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_d89386d1-b508-4b06-9e23-b21fef2cbca5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_6013593f-5730-4e29-939e-f16060341492" xlink:to="loc_us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_d89386d1-b508-4b06-9e23-b21fef2cbca5" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_d116f430-7675-483b-a92f-cb7655a2ade0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_6013593f-5730-4e29-939e-f16060341492" xlink:to="loc_us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_d116f430-7675-483b-a92f-cb7655a2ade0" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeasePayments_62b805e3-0939-4059-8a20-072c4a3cd8d0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingLeasePayments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_6013593f-5730-4e29-939e-f16060341492" xlink:to="loc_us-gaap_OperatingLeasePayments_62b805e3-0939-4059-8a20-072c4a3cd8d0" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseExpense_19f0207f-2f82-4b84-94ba-3ea5bc07db6d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingLeaseExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_6013593f-5730-4e29-939e-f16060341492" xlink:to="loc_us-gaap_OperatingLeaseExpense_19f0207f-2f82-4b84-94ba-3ea5bc07db6d" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_LesseeOperatingLeaseLiabilityToBePaidIncreaseInInitialBaseRentPercent_8a131603-4998-4909-8f45-e451265df039" xlink:href="ngm-20230630.xsd#ngm_LesseeOperatingLeaseLiabilityToBePaidIncreaseInInitialBaseRentPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_6013593f-5730-4e29-939e-f16060341492" xlink:to="loc_ngm_LesseeOperatingLeaseLiabilityToBePaidIncreaseInInitialBaseRentPercent_8a131603-4998-4909-8f45-e451265df039" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_LesseeOperatingLeaseTenantImprovementAllowance_924df4c6-18ba-4d9f-9bb8-7b2374b117dd" xlink:href="ngm-20230630.xsd#ngm_LesseeOperatingLeaseTenantImprovementAllowance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_6013593f-5730-4e29-939e-f16060341492" xlink:to="loc_ngm_LesseeOperatingLeaseTenantImprovementAllowance_924df4c6-18ba-4d9f-9bb8-7b2374b117dd" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseRenewalTerm_afc9d185-06a9-4547-9c1c-ed40ac16b55b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LesseeOperatingLeaseRenewalTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_6013593f-5730-4e29-939e-f16060341492" xlink:to="loc_us-gaap_LesseeOperatingLeaseRenewalTerm_afc9d185-06a9-4547-9c1c-ed40ac16b55b" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LettersOfCreditOutstandingAmount_29cccf1e-f441-48b6-a568-11112a6e92e3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LettersOfCreditOutstandingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_6013593f-5730-4e29-939e-f16060341492" xlink:to="loc_us-gaap_LettersOfCreditOutstandingAmount_29cccf1e-f441-48b6-a568-11112a6e92e3" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseByMajorPropertyClassTable_1c67dc0f-8c5e-4b7d-ab1b-7901cd902cbc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertySubjectToOrAvailableForOperatingLeaseByMajorPropertyClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_6013593f-5730-4e29-939e-f16060341492" xlink:to="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseByMajorPropertyClassTable_1c67dc0f-8c5e-4b7d-ab1b-7901cd902cbc" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_f3e5a49d-e72a-4b25-a937-2842890d3d85" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseByMajorPropertyClassTable_1c67dc0f-8c5e-4b7d-ab1b-7901cd902cbc" xlink:to="loc_us-gaap_CreditFacilityAxis_f3e5a49d-e72a-4b25-a937-2842890d3d85" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_f3e5a49d-e72a-4b25-a937-2842890d3d85_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_f3e5a49d-e72a-4b25-a937-2842890d3d85" xlink:to="loc_us-gaap_CreditFacilityDomain_f3e5a49d-e72a-4b25-a937-2842890d3d85_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_5f2f6c42-2fec-4aea-bfd0-95160c515a7c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_f3e5a49d-e72a-4b25-a937-2842890d3d85" xlink:to="loc_us-gaap_CreditFacilityDomain_5f2f6c42-2fec-4aea-bfd0-95160c515a7c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LetterOfCreditMember_8f55a1ed-b7f1-4915-9dd6-5f697a1b03fa" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LetterOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_5f2f6c42-2fec-4aea-bfd0-95160c515a7c" xlink:to="loc_us-gaap_LetterOfCreditMember_8f55a1ed-b7f1-4915-9dd6-5f697a1b03fa" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_OperatingLeaseExpenseTermAxis_a5ee6d26-7fd8-4137-adab-1956d0028d90" xlink:href="ngm-20230630.xsd#ngm_OperatingLeaseExpenseTermAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseByMajorPropertyClassTable_1c67dc0f-8c5e-4b7d-ab1b-7901cd902cbc" xlink:to="loc_ngm_OperatingLeaseExpenseTermAxis_a5ee6d26-7fd8-4137-adab-1956d0028d90" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_OperatingLeaseExpenseTermDomain_a5ee6d26-7fd8-4137-adab-1956d0028d90_default" xlink:href="ngm-20230630.xsd#ngm_OperatingLeaseExpenseTermDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_ngm_OperatingLeaseExpenseTermAxis_a5ee6d26-7fd8-4137-adab-1956d0028d90" xlink:to="loc_ngm_OperatingLeaseExpenseTermDomain_a5ee6d26-7fd8-4137-adab-1956d0028d90_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_OperatingLeaseExpenseTermDomain_ea0f9d59-c24d-46f0-9ddf-33d7293ccdd5" xlink:href="ngm-20230630.xsd#ngm_OperatingLeaseExpenseTermDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_ngm_OperatingLeaseExpenseTermAxis_a5ee6d26-7fd8-4137-adab-1956d0028d90" xlink:to="loc_ngm_OperatingLeaseExpenseTermDomain_ea0f9d59-c24d-46f0-9ddf-33d7293ccdd5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_OperatingLeaseExpenseMonthlyTermMember_756dad65-9026-4a49-a7d0-8d4abf937220" xlink:href="ngm-20230630.xsd#ngm_OperatingLeaseExpenseMonthlyTermMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ngm_OperatingLeaseExpenseTermDomain_ea0f9d59-c24d-46f0-9ddf-33d7293ccdd5" xlink:to="loc_ngm_OperatingLeaseExpenseMonthlyTermMember_756dad65-9026-4a49-a7d0-8d4abf937220" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_OperatingLeaseExpenseContractTermMember_571343da-bd02-46dd-bf91-bb6c8b405e19" xlink:href="ngm-20230630.xsd#ngm_OperatingLeaseExpenseContractTermMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ngm_OperatingLeaseExpenseTermDomain_ea0f9d59-c24d-46f0-9ddf-33d7293ccdd5" xlink:to="loc_ngm_OperatingLeaseExpenseContractTermMember_571343da-bd02-46dd-bf91-bb6c8b405e19" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_2a7d4c55-1bb0-4646-b5dc-e10820468d1e" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseByMajorPropertyClassTable_1c67dc0f-8c5e-4b7d-ab1b-7901cd902cbc" xlink:to="loc_srt_RangeAxis_2a7d4c55-1bb0-4646-b5dc-e10820468d1e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_2a7d4c55-1bb0-4646-b5dc-e10820468d1e_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_2a7d4c55-1bb0-4646-b5dc-e10820468d1e" xlink:to="loc_srt_RangeMember_2a7d4c55-1bb0-4646-b5dc-e10820468d1e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_4a6e065d-c6d0-4335-870f-11b84c495279" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_2a7d4c55-1bb0-4646-b5dc-e10820468d1e" xlink:to="loc_srt_RangeMember_4a6e065d-c6d0-4335-870f-11b84c495279" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_2b07cd5b-2cab-4434-bdb0-4496e6bb92eb" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_4a6e065d-c6d0-4335-870f-11b84c495279" xlink:to="loc_srt_MinimumMember_2b07cd5b-2cab-4434-bdb0-4496e6bb92eb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_fdcc1f32-9ee0-4e3c-8abb-881eb3d72861" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_4a6e065d-c6d0-4335-870f-11b84c495279" xlink:to="loc_srt_MaximumMember_fdcc1f32-9ee0-4e3c-8abb-881eb3d72861" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeAxis_b68943ad-9e6f-4f9c-9344-bb0a2293ec57" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShortTermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseByMajorPropertyClassTable_1c67dc0f-8c5e-4b7d-ab1b-7901cd902cbc" xlink:to="loc_us-gaap_ShortTermDebtTypeAxis_b68943ad-9e6f-4f9c-9344-bb0a2293ec57" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeDomain_b68943ad-9e6f-4f9c-9344-bb0a2293ec57_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShortTermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ShortTermDebtTypeAxis_b68943ad-9e6f-4f9c-9344-bb0a2293ec57" xlink:to="loc_us-gaap_ShortTermDebtTypeDomain_b68943ad-9e6f-4f9c-9344-bb0a2293ec57_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeDomain_858399f5-dc5b-4da8-a29e-945de5bfe09e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShortTermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ShortTermDebtTypeAxis_b68943ad-9e6f-4f9c-9344-bb0a2293ec57" xlink:to="loc_us-gaap_ShortTermDebtTypeDomain_858399f5-dc5b-4da8-a29e-945de5bfe09e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LetterOfCreditMember_9e24fbdf-71d8-4bd1-8af3-e1e4478e6d8a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LetterOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShortTermDebtTypeDomain_858399f5-dc5b-4da8-a29e-945de5bfe09e" xlink:to="loc_us-gaap_LetterOfCreditMember_9e24fbdf-71d8-4bd1-8af3-e1e4478e6d8a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeaseContractualTermAxis_0d1ea000-ccfb-426d-82e7-83fb4b7aabe8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LeaseContractualTermAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseByMajorPropertyClassTable_1c67dc0f-8c5e-4b7d-ab1b-7901cd902cbc" xlink:to="loc_us-gaap_LeaseContractualTermAxis_0d1ea000-ccfb-426d-82e7-83fb4b7aabe8" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeaseContractualTermDomain_0d1ea000-ccfb-426d-82e7-83fb4b7aabe8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LeaseContractualTermDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LeaseContractualTermAxis_0d1ea000-ccfb-426d-82e7-83fb4b7aabe8" xlink:to="loc_us-gaap_LeaseContractualTermDomain_0d1ea000-ccfb-426d-82e7-83fb4b7aabe8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeaseContractualTermDomain_9e6de33a-2881-4857-8da8-a5e597226835" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LeaseContractualTermDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LeaseContractualTermAxis_0d1ea000-ccfb-426d-82e7-83fb4b7aabe8" xlink:to="loc_us-gaap_LeaseContractualTermDomain_9e6de33a-2881-4857-8da8-a5e597226835" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_CorporateOfficeSpaceAndLaboratoryFacilityMember_2bccd77e-4ec3-4e18-93ee-ebbe7d6a12be" xlink:href="ngm-20230630.xsd#ngm_CorporateOfficeSpaceAndLaboratoryFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LeaseContractualTermDomain_9e6de33a-2881-4857-8da8-a5e597226835" xlink:to="loc_ngm_CorporateOfficeSpaceAndLaboratoryFacilityMember_2bccd77e-4ec3-4e18-93ee-ebbe7d6a12be" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_5ca034ec-131c-4d73-bcef-ce7982810a92" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseByMajorPropertyClassTable_1c67dc0f-8c5e-4b7d-ab1b-7901cd902cbc" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_5ca034ec-131c-4d73-bcef-ce7982810a92" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_5ca034ec-131c-4d73-bcef-ce7982810a92_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_5ca034ec-131c-4d73-bcef-ce7982810a92" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_5ca034ec-131c-4d73-bcef-ce7982810a92_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_2b2afb17-0ac9-4af6-bccc-8328804cc6a9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_5ca034ec-131c-4d73-bcef-ce7982810a92" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_2b2afb17-0ac9-4af6-bccc-8328804cc6a9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeaseholdImprovementsMember_8fd09f6d-ec68-444f-bcda-80212e5eb985" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LeaseholdImprovementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_2b2afb17-0ac9-4af6-bccc-8328804cc6a9" xlink:to="loc_us-gaap_LeaseholdImprovementsMember_8fd09f6d-ec68-444f-bcda-80212e5eb985" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ngmbio.com/role/StockBasedCompensationNarrativeDetails" xlink:type="simple" xlink:href="ngm-20230630.xsd#StockBasedCompensationNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.ngmbio.com/role/StockBasedCompensationNarrativeDetails" xlink:type="extended" id="i9462322ba8d7474f8d17561f0c057aee_StockBasedCompensationNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockLineItems_acf379d5-6a06-466a-aebb-66be577ed103" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_812cfff9-df3b-4f6e-b1f1-d71ca6f26062" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_acf379d5-6a06-466a-aebb-66be577ed103" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_812cfff9-df3b-4f6e-b1f1-d71ca6f26062" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumEmployeeSubscriptionRate_d679e8f4-c7fd-4713-ab6a-b910b47d873f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumEmployeeSubscriptionRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_acf379d5-6a06-466a-aebb-66be577ed103" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumEmployeeSubscriptionRate_d679e8f4-c7fd-4713-ab6a-b910b47d873f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_ShareBasedCompensationArrangementByShareBasedPaymentAwardOfferingPeriod_6f81a578-7963-455c-ab65-4fe80ba4c26f" xlink:href="ngm-20230630.xsd#ngm_ShareBasedCompensationArrangementByShareBasedPaymentAwardOfferingPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_acf379d5-6a06-466a-aebb-66be577ed103" xlink:to="loc_ngm_ShareBasedCompensationArrangementByShareBasedPaymentAwardOfferingPeriod_6f81a578-7963-455c-ab65-4fe80ba4c26f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfPurchasePeriods_98cdc102-a4d3-4fc5-8d3f-75dc0decb0ea" xlink:href="ngm-20230630.xsd#ngm_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfPurchasePeriods"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_acf379d5-6a06-466a-aebb-66be577ed103" xlink:to="loc_ngm_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfPurchasePeriods_98cdc102-a4d3-4fc5-8d3f-75dc0decb0ea" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_ShareBasedCompensationArrangementByShareBasedPaymentAwardPurchasePeriodTerm_8c6466db-9fbc-40f6-a6c5-6127fb2f26ac" xlink:href="ngm-20230630.xsd#ngm_ShareBasedCompensationArrangementByShareBasedPaymentAwardPurchasePeriodTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_acf379d5-6a06-466a-aebb-66be577ed103" xlink:to="loc_ngm_ShareBasedCompensationArrangementByShareBasedPaymentAwardPurchasePeriodTerm_8c6466db-9fbc-40f6-a6c5-6127fb2f26ac" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPriceOfferingDate_f29b99d5-2d5c-4e4a-bb87-9ad0c1ea5b91" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPriceOfferingDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_acf379d5-6a06-466a-aebb-66be577ed103" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPriceOfferingDate_f29b99d5-2d5c-4e4a-bb87-9ad0c1ea5b91" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_35f0d7ef-6710-42b6-83bf-8b87c193f1f6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_acf379d5-6a06-466a-aebb-66be577ed103" xlink:to="loc_us-gaap_CommonStockSharesIssued_35f0d7ef-6710-42b6-83bf-8b87c193f1f6" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_3eecd67b-2b0f-4a3e-9fd8-9624dd598673" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_acf379d5-6a06-466a-aebb-66be577ed103" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_3eecd67b-2b0f-4a3e-9fd8-9624dd598673" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_d0f6a116-a732-4ed1-93b3-4383038ed54d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_acf379d5-6a06-466a-aebb-66be577ed103" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_d0f6a116-a732-4ed1-93b3-4383038ed54d" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_816756d4-cdf9-4cb8-b58d-0774dd5febd2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_acf379d5-6a06-466a-aebb-66be577ed103" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_816756d4-cdf9-4cb8-b58d-0774dd5febd2" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_30e34aa7-ca6a-458c-a3e4-1ab1fc648112" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_acf379d5-6a06-466a-aebb-66be577ed103" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_30e34aa7-ca6a-458c-a3e4-1ab1fc648112" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_da4bb5ba-4eb0-4f10-9e9e-1ba94b109b75" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_acf379d5-6a06-466a-aebb-66be577ed103" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_da4bb5ba-4eb0-4f10-9e9e-1ba94b109b75" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_047daeab-1ced-4f4d-acd0-ec0ef3713188" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_acf379d5-6a06-466a-aebb-66be577ed103" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_047daeab-1ced-4f4d-acd0-ec0ef3713188" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_42590b42-9505-42e3-9a66-4535af470144" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_acf379d5-6a06-466a-aebb-66be577ed103" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_42590b42-9505-42e3-9a66-4535af470144" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_022c4b8e-0b5b-4517-91bc-e656f9978e4b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_acf379d5-6a06-466a-aebb-66be577ed103" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_022c4b8e-0b5b-4517-91bc-e656f9978e4b" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_37583ed3-75f1-4474-8ce7-3011d4003c2d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfStockByClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_acf379d5-6a06-466a-aebb-66be577ed103" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_37583ed3-75f1-4474-8ce7-3011d4003c2d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_e13c3696-96e2-4f3d-82ac-6d170bf272ab" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsidiarySaleOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_37583ed3-75f1-4474-8ce7-3011d4003c2d" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_e13c3696-96e2-4f3d-82ac-6d170bf272ab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_e13c3696-96e2-4f3d-82ac-6d170bf272ab_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_e13c3696-96e2-4f3d-82ac-6d170bf272ab" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_e13c3696-96e2-4f3d-82ac-6d170bf272ab_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_8f562ab3-a9d2-4f17-adc3-73f9c9fa196e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_e13c3696-96e2-4f3d-82ac-6d170bf272ab" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_8f562ab3-a9d2-4f17-adc3-73f9c9fa196e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockMember_713343a2-9f20-4e17-a963-2e02f4930f2f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_8f562ab3-a9d2-4f17-adc3-73f9c9fa196e" xlink:to="loc_us-gaap_EmployeeStockMember_713343a2-9f20-4e17-a963-2e02f4930f2f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_d8dad73a-2fc3-42e3-a4bf-3e82a0c78457" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_37583ed3-75f1-4474-8ce7-3011d4003c2d" xlink:to="loc_us-gaap_AwardTypeAxis_d8dad73a-2fc3-42e3-a4bf-3e82a0c78457" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_d8dad73a-2fc3-42e3-a4bf-3e82a0c78457_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_d8dad73a-2fc3-42e3-a4bf-3e82a0c78457" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_d8dad73a-2fc3-42e3-a4bf-3e82a0c78457_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_cfe30f99-def4-4b1b-9ec9-d747aea164dc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_d8dad73a-2fc3-42e3-a4bf-3e82a0c78457" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_cfe30f99-def4-4b1b-9ec9-d747aea164dc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_d666ed6f-0ffa-455a-9745-6d8cc7484655" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_cfe30f99-def4-4b1b-9ec9-d747aea164dc" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_d666ed6f-0ffa-455a-9745-6d8cc7484655" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_ab245c76-03db-4350-9d18-85db073e1527" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_cfe30f99-def4-4b1b-9ec9-d747aea164dc" xlink:to="loc_us-gaap_EmployeeStockOptionMember_ab245c76-03db-4350-9d18-85db073e1527" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveAxis_ffff6662-23c2-409d-b7fd-c2c3896a736e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestructuringCostAndReserveAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_37583ed3-75f1-4474-8ce7-3011d4003c2d" xlink:to="loc_us-gaap_RestructuringCostAndReserveAxis_ffff6662-23c2-409d-b7fd-c2c3896a736e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_ffff6662-23c2-409d-b7fd-c2c3896a736e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TypeOfRestructuringDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_ffff6662-23c2-409d-b7fd-c2c3896a736e" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_ffff6662-23c2-409d-b7fd-c2c3896a736e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_8d5f1634-f6b4-4720-a6fd-1dbb0007408d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TypeOfRestructuringDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_ffff6662-23c2-409d-b7fd-c2c3896a736e" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_8d5f1634-f6b4-4720-a6fd-1dbb0007408d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_ShareBasedCompensationMember_095d6504-5cd6-48c5-8247-69983226e1a0" xlink:href="ngm-20230630.xsd#ngm_ShareBasedCompensationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_8d5f1634-f6b4-4720-a6fd-1dbb0007408d" xlink:to="loc_ngm_ShareBasedCompensationMember_095d6504-5cd6-48c5-8247-69983226e1a0" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ngmbio.com/role/StockBasedCompensationScheduleofStockBasedCompensationExpenseDetails" xlink:type="simple" xlink:href="ngm-20230630.xsd#StockBasedCompensationScheduleofStockBasedCompensationExpenseDetails"/>
  <link:definitionLink xlink:role="http://www.ngmbio.com/role/StockBasedCompensationScheduleofStockBasedCompensationExpenseDetails" xlink:type="extended" id="i978b3d3d414d4a339ca2e7505c9a620e_StockBasedCompensationScheduleofStockBasedCompensationExpenseDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_3c7f84a7-fe5e-421c-9b71-0ba3d9fa1933" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_9c087b38-27fc-4030-9f7e-efc43ecb64e6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_3c7f84a7-fe5e-421c-9b71-0ba3d9fa1933" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_9c087b38-27fc-4030-9f7e-efc43ecb64e6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_5668fe28-a911-4b37-b2c7-e5909492a36a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_3c7f84a7-fe5e-421c-9b71-0ba3d9fa1933" xlink:to="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_5668fe28-a911-4b37-b2c7-e5909492a36a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_TitleOfIndividualAxis_03f5258b-63c3-4cca-a1fd-0b5d24862559" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_TitleOfIndividualAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_5668fe28-a911-4b37-b2c7-e5909492a36a" xlink:to="loc_srt_TitleOfIndividualAxis_03f5258b-63c3-4cca-a1fd-0b5d24862559" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_03f5258b-63c3-4cca-a1fd-0b5d24862559_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_TitleOfIndividualWithRelationshipToEntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_TitleOfIndividualAxis_03f5258b-63c3-4cca-a1fd-0b5d24862559" xlink:to="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_03f5258b-63c3-4cca-a1fd-0b5d24862559_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_d2c843fd-4438-435e-943a-bf313874de0f" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_TitleOfIndividualWithRelationshipToEntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_TitleOfIndividualAxis_03f5258b-63c3-4cca-a1fd-0b5d24862559" xlink:to="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_d2c843fd-4438-435e-943a-bf313874de0f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_EmployeesAndDirectorsMember_cd09a0a3-bdc3-48c3-b29b-bb466f403cdb" xlink:href="ngm-20230630.xsd#ngm_EmployeesAndDirectorsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_TitleOfIndividualWithRelationshipToEntityDomain_d2c843fd-4438-435e-943a-bf313874de0f" xlink:to="loc_ngm_EmployeesAndDirectorsMember_cd09a0a3-bdc3-48c3-b29b-bb466f403cdb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_c5ad7b2c-91ac-4a8d-838e-83af2d749ffd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_5668fe28-a911-4b37-b2c7-e5909492a36a" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_c5ad7b2c-91ac-4a8d-838e-83af2d749ffd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_c5ad7b2c-91ac-4a8d-838e-83af2d749ffd_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_c5ad7b2c-91ac-4a8d-838e-83af2d749ffd" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_c5ad7b2c-91ac-4a8d-838e-83af2d749ffd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_19d4343d-8b69-4f7f-a8d3-4dee452974e2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_c5ad7b2c-91ac-4a8d-838e-83af2d749ffd" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_19d4343d-8b69-4f7f-a8d3-4dee452974e2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpenseMember_44f13ce9-b7f2-47e9-859b-4b53362410c1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ResearchAndDevelopmentExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_19d4343d-8b69-4f7f-a8d3-4dee452974e2" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpenseMember_44f13ce9-b7f2-47e9-859b-4b53362410c1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpenseMember_c5b805ff-7356-4dfa-93ec-a15314ff7074" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GeneralAndAdministrativeExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_19d4343d-8b69-4f7f-a8d3-4dee452974e2" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpenseMember_c5b805ff-7356-4dfa-93ec-a15314ff7074" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.ngmbio.com/role/WorkforceReductionDetails" xlink:type="simple" xlink:href="ngm-20230630.xsd#WorkforceReductionDetails"/>
  <link:definitionLink xlink:role="http://www.ngmbio.com/role/WorkforceReductionDetails" xlink:type="extended" id="ia35b44250a2a4c86ae2543d0626f31c9_WorkforceReductionDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveLineItems_cd237585-5f7a-43a8-8aeb-98e50b96059e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestructuringCostAndReserveLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringAndRelatedCostExpectedNumberOfPositionsEliminated_4903cb54-52fc-47d8-b2fd-07b0631e8385" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestructuringAndRelatedCostExpectedNumberOfPositionsEliminated"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_cd237585-5f7a-43a8-8aeb-98e50b96059e" xlink:to="loc_us-gaap_RestructuringAndRelatedCostExpectedNumberOfPositionsEliminated_4903cb54-52fc-47d8-b2fd-07b0631e8385" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringAndRelatedCostNumberOfPositionsEliminatedPeriodPercent_0da7e9d1-0867-453f-8257-bb3e502e4f3f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestructuringAndRelatedCostNumberOfPositionsEliminatedPeriodPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_cd237585-5f7a-43a8-8aeb-98e50b96059e" xlink:to="loc_us-gaap_RestructuringAndRelatedCostNumberOfPositionsEliminatedPeriodPercent_0da7e9d1-0867-453f-8257-bb3e502e4f3f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCharges_9b3eeaa0-7de4-488c-9b35-78be97a5133e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestructuringCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_cd237585-5f7a-43a8-8aeb-98e50b96059e" xlink:to="loc_us-gaap_RestructuringCharges_9b3eeaa0-7de4-488c-9b35-78be97a5133e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_24db14b1-77b6-4c8d-aefc-7a59703ac17d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfRestructuringAndRelatedCostsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_cd237585-5f7a-43a8-8aeb-98e50b96059e" xlink:to="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_24db14b1-77b6-4c8d-aefc-7a59703ac17d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveAxis_9ea07cdf-462d-4a78-a3df-0cafb70d7541" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestructuringCostAndReserveAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_24db14b1-77b6-4c8d-aefc-7a59703ac17d" xlink:to="loc_us-gaap_RestructuringCostAndReserveAxis_9ea07cdf-462d-4a78-a3df-0cafb70d7541" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_9ea07cdf-462d-4a78-a3df-0cafb70d7541_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TypeOfRestructuringDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_9ea07cdf-462d-4a78-a3df-0cafb70d7541" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_9ea07cdf-462d-4a78-a3df-0cafb70d7541_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_062c0a1a-4fea-4697-8569-b2dc747a1aa1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TypeOfRestructuringDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_9ea07cdf-462d-4a78-a3df-0cafb70d7541" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_062c0a1a-4fea-4697-8569-b2dc747a1aa1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeSeveranceMember_dae5af65-ea41-4e96-8154-fa701117437c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeSeveranceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_062c0a1a-4fea-4697-8569-b2dc747a1aa1" xlink:to="loc_us-gaap_EmployeeSeveranceMember_dae5af65-ea41-4e96-8154-fa701117437c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngm_ShareBasedCompensationMember_452b9cbd-adea-49af-898f-2633ee1754f4" xlink:href="ngm-20230630.xsd#ngm_ShareBasedCompensationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_062c0a1a-4fea-4697-8569-b2dc747a1aa1" xlink:to="loc_ngm_ShareBasedCompensationMember_452b9cbd-adea-49af-898f-2633ee1754f4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_f0fb2327-0d64-4846-a007-9e2222d7afe0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_24db14b1-77b6-4c8d-aefc-7a59703ac17d" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_f0fb2327-0d64-4846-a007-9e2222d7afe0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_f0fb2327-0d64-4846-a007-9e2222d7afe0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_f0fb2327-0d64-4846-a007-9e2222d7afe0" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_f0fb2327-0d64-4846-a007-9e2222d7afe0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_52a3eda6-8746-4317-905d-895753f132a9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_f0fb2327-0d64-4846-a007-9e2222d7afe0" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_52a3eda6-8746-4317-905d-895753f132a9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpenseMember_ae92a6a6-d595-4984-beeb-0d6411bb0248" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ResearchAndDevelopmentExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_52a3eda6-8746-4317-905d-895753f132a9" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpenseMember_ae92a6a6-d595-4984-beeb-0d6411bb0248" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpenseMember_680d5a5b-5389-4849-b438-7f72d23959e4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GeneralAndAdministrativeExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_52a3eda6-8746-4317-905d-895753f132a9" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpenseMember_680d5a5b-5389-4849-b438-7f72d23959e4" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://xbrl.sec.gov/ecd/AwardTypeOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2023/ecd-2023.xsd#AwardTypeOnly"/>
  <link:definitionLink xlink:role="http://xbrl.sec.gov/ecd/AwardTypeOnly" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember" xlink:type="arc" order="4"/>
  </link:definitionLink>
</link:linkbase>
