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

    <schemaVersion>X0609</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2026-07-16</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>true</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2026-07-16</value>
            </transactionDate>
            <deemedExecutionDate>
                <value>2026-07-16</value>
            </deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>10</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>13.73</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2857490</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Reflects 2,857,500 shares of Common Stock beneficially owned by the Reporting Person immediately prior to the reported transaction, less the 10 shares sold.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Innovative Cellular Therapeutics Holdings Limited
By: /s/ Lei Xiao
Name: Lei Xiao
Title: Chief Executive Officer</signatureName>
        <signatureDate>2026-07-17</signatureDate>
    </ownerSignature>
</ownershipDocument>
