<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2025-11-20</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001047127</issuerCik>
        <issuerName>AMKOR TECHNOLOGY, INC.</issuerName>
        <issuerTradingSymbol>AMKR</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0002034104</rptOwnerCik>
            <rptOwnerName>2024 Grantor Retained Annuity Trust of Agnes C. Kim dtd. 8/5/2024</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O SIANA CARR O'CONNOR &amp; LYNAM</rptOwnerStreet1>
            <rptOwnerStreet2>1500 EAST LANCASTER AVENUE</rptOwnerStreet2>
            <rptOwnerCity>PAOLI</rptOwnerCity>
            <rptOwnerState>PA</rptOwnerState>
            <rptOwnerZipCode>19301-9713</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>1</isOther>
            <otherText>Member of 10% owner group (2)</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2025-11-20</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>G</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>705000</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>895000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">On November 20, 2025, the 2024 Grantor Retained Annuity Trust of Agnes C. Kim 8/5/2024
distributed 705,000 shares of the Common Stock of Amkor Technology, Inc (the &quot;Issuer&quot;) to the Agnes C. Kim Revocable Trust, of which Agnes C. Kim is the sole settlor, sole beneficiary, and sole trustee. Susan Y. Kim is the sole trustee of the 2024 Grantor Retained Annuity Trust of Agnes C. Kim 8/5/2024.</footnote>
    </footnotes>

    <remarks>2. The Reporting Person disclaims beneficial ownership of these securities, except to the extent of the Reporting Person's pecuniary interest therein, and this report shall not be deemed an admission that the Reporting Person is the beneficial owner of such securities, except to the extent of the Reporting Person's pecuniary interest therein, for purposes of Section 16 of the Securities Exchange Act of 1934, as amended (&quot;Section 16&quot;), or for any other purpose.</remarks>

    <ownerSignature>
        <signatureName>/s/ Brian D. Short, Attorney-in-Fact for Agnes C. Kim</signatureName>
        <signatureDate>2025-11-24</signatureDate>
    </ownerSignature>
</ownershipDocument>
