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

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2025-10-16</periodOfReport>

    <issuer>
        <issuerCik>0001389545</issuerCik>
        <issuerName>NovaBay Pharmaceuticals, Inc.</issuerName>
        <issuerTradingSymbol>NBY</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0002091727</rptOwnerCik>
            <rptOwnerName>Kazley Michael John</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1111 LINCOLN ROAD, SUITE 500</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>MIAMI BEACH</rptOwnerCity>
            <rptOwnerState>FL</rptOwnerState>
            <rptOwnerZipCode>33139</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <officerTitle>Chief Executive Officer</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2025-10-21</value>
                <footnoteId id="F1"/>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>C</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>56806080</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>56806080</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By R01 Entities</value>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Pre-Funded Warrants (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>0.01</value>
                <footnoteId id="F3"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2025-10-16</value>
                <footnoteId id="F3"/>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>2702703</value>
                    <footnoteId id="F3"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2026-01-01</value>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F3"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>2702703</value>
                    <footnoteId id="F3"/>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2702703</value>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By R01 Entities</value>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">This represents (i) the conversion of 220,663 shares of the Issuer's Series D Non-Voting Convertible Preferred Stock, par value $0.01 per share (the &quot;Series D Preferred Stock&quot;) into 35,306,080 shares of the Issuer's common stock, par value $0.01 per share (the &quot;Common Stock&quot;) and (ii) the conversion of 134,375 shares of the Issuer's Series E Non-Voting Convertible Preferred Stock, par value $0.01 per share (the &quot;Series E Preferred Stock&quot;) into 21,500,000 shares of the Issuer's Common Stock, both of which occurred on October 21, 2025 following stockholder approval at the Issuer's annual meeting on October 16, 2025 of proposals 5 and 9 set forth in the Issuer's Definitive Proxy Statement on Schedule 14A, filed by the Issuer with the Securities and Exchange Commission on September 23, 2025.</footnote>
        <footnote id="F2">The reported securities may also be deemed to be beneficially owned by R01 Fund LP (&quot;R01 LP&quot;), R01 Capital LLC (&quot;R01 Capital&quot;) and R01 Capital Manager LLC (&quot;R01 Capital Manager&quot; and together with R01 LP, R01 Capital and the Reporting Person, the &quot;R01 Entities&quot;), each of which or whom disclaim beneficial ownership of these shares, except to the extent of its or his pecuniary interest in such shares, if any. R01 Capital is the general partner of R01 LP. R01 Capital Manager is the investment manager for R01 Capital. The Reporting Person is the managing member of R01 Capital Manager.</footnote>
        <footnote id="F3">On October 16, 2025, the Issuer issued and sold to R01 LP pre-funded warrants (the &quot;Pre-Funded Warrants&quot;) to purchase an aggregate 2,702,703 shares of the Issuer's Common Stock. The purchase price was $1.10 per warrant, representing 110% of the closing price of the Common Stock on the day before the issuance, less the $0.01 exercise price for each warrant. The Pre-Funded Warrants have no expiration date and are exercisable for shares of Common Stock at any time after January 1, 2026, subject to receipt of stockholder approval.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Michael Kazley</signatureName>
        <signatureDate>2025-11-03</signatureDate>
    </ownerSignature>
</ownershipDocument>
