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

    <schemaVersion>X0206</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2026-02-26</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0002101135</issuerCik>
        <issuerName>Illumination Acquisition Corp. I</issuerName>
        <issuerTradingSymbol>ILLU</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0002101134</rptOwnerCik>
            <rptOwnerName>Illumination Acquisition 1 Sponsor LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O ILLUMINATION ACQUISITION CORP I</rptOwnerStreet1>
            <rptOwnerStreet2>570 LEXINGTON AVENUE, 40TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10022</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001383194</rptOwnerCik>
            <rptOwnerName>LIPMAN JOHN C</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O ILLUMINATION ACQUISITION CORP I</rptOwnerStreet1>
            <rptOwnerStreet2>40TH FLOOR, 570 LEXINGTON AVENUE</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10022</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>CEO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001842508</rptOwnerCik>
            <rptOwnerName>Rosenberg David I.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O ILLUMINATION ACQUISITION CORP I</rptOwnerStreet1>
            <rptOwnerStreet2>40TH FLOOR, 570 LEXINGTON AVENUE</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10022</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chairman</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Class A Ordinary Shares</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>365000</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Illumination Acquisition 1 Sponsor LLC</value>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Class B Ordinary Shares</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>0</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F3"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Class A Ordinary Shares</value>
                    <footnoteId id="F3"/>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>7666667</value>
                    <footnoteId id="F4"/>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Illumination Acquisition 1 Sponsor LLC</value>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Warrant</value>
                <footnoteId id="F5"/>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>11.50</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F6"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F7"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Class A Ordinary Shares</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>121667</value>
                    <footnoteId id="F8"/>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Illumination Acquisition 1 Sponsor LLC</value>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Represents 365,000 Class A ordinary shares contained within units that the reporting person has irrevocably agreed to purchase at the closing of the Issuer's initial public offering (the &quot;IPO&quot;). Does not include up to an additional 30,000 Class A ordinary shares contained within units that the reporting person has irrevocably agreed to purchase in connection with the IPO if and only if the underwriters of the IPO fully exercise their over-allotment option.</footnote>
        <footnote id="F2">Represents securities held by Illumination Acquisition 1 Sponsor LLC. John Lipman and David I. Rosenberg indirectly control the management of such entity, including the exercise of voting and investment discretion with respect to the securities held of record by such entity.</footnote>
        <footnote id="F3">The Class B ordinary shares of the Issuer are convertible into the Issuer's Class A ordinary shares concurrently with or immediately following the consummation of an initial business combination, or earlier at the option of the holders thereof on a one-for-one basis, subject to the adjustments.  The Class B ordinary shares have no expiration date.</footnote>
        <footnote id="F4">Includes up to 1,000,000 Class A ordinary shares issuable upon conversion of Class B ordinary shares that are subject to forfeiture in the event the underwriters of the Issuer's IPO do not exercise their over-allotment option in full.</footnote>
        <footnote id="F5">Represents warrants contained within units that the reporting person has irrevocably agreed to purchase at the closing of the Issuer's IPO.</footnote>
        <footnote id="F6">Each warrant will become exercisable at the later of 12 months from the closing of the IPO and 30 days after the completion of the Issuer's initial business combination.</footnote>
        <footnote id="F7">Each warrant will expire five years after the completion of the Issuer's initial business combination or earlier upon redemption or the Issuer's liquidation.</footnote>
        <footnote id="F8">Does not include up to an additional 10,000 Class A ordinary shares underlying warrants contained within units that the reporting person has irrevocably agreed to purchase in connection with the IPO if and only if the underwriters of the IPO fully exercise their over-allotment option.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Illumination Acquisition 1 Sponsor LLC by John Lipman, Managing Member</signatureName>
        <signatureDate>2026-02-26</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ John Lipman</signatureName>
        <signatureDate>2026-02-26</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ David Rosenberg</signatureName>
        <signatureDate>2026-02-26</signatureDate>
    </ownerSignature>
</ownershipDocument>
