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

    <schemaVersion>X0609</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2026-06-15</periodOfReport>

    <issuer>
        <issuerCik>0001806952</issuerCik>
        <issuerName>Lyell Immunopharma, Inc.</issuerName>
        <issuerTradingSymbol>LYEL</issuerTradingSymbol>
        <issuerForeignTradingSymbol></issuerForeignTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0002095697</rptOwnerCik>
            <rptOwnerName>Innovative Cellular Therapeutics Holdings Ltd</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerNonUSAddressFlag>true</rptOwnerNonUSAddressFlag>
            <rptOwnerStreet1>190 ELGIN AVENUE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>GEORGE TOWN</rptOwnerCity>
            <rptOwnerNonUSStateTerritory></rptOwnerNonUSStateTerritory>
            <rptOwnerCountry>E9</rptOwnerCountry>
            <rptOwnerZipCode>KY1-9008</rptOwnerZipCode>
            <rptOwnerStateDescription>CAYMAN ISLANDS</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isTenPercentOwner>true</isTenPercentOwner>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>false</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2026-06-15</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>66500</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2933500</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Represents shares of Common Stock transferred by the Reporting Person to LifeSci Advisors, LLC as broker commission in connection with the Upfront Payment (as such term is defined in the License Agreement, dated November 6, 2025, between the Issuer and the Reporting Person). The transaction was a transfer of securities for no cash consideration to the Reporting Person and is reported under transaction code J.</footnote>
        <footnote id="F2">Reflects 3,000,000 shares of Common Stock beneficially owned by the Reporting Person immediately prior to the reported transaction, less the 66,500 shares transferred. All shares are held directly and registered in the name of the Reporting Person.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Lei Xiao, Chief Executive Officer</signatureName>
        <signatureDate>2026-06-18</signatureDate>
    </ownerSignature>
</ownershipDocument>
