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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2021-03-02</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001651052</issuerCik>
        <issuerName>Focus Financial Partners Inc.</issuerName>
        <issuerTradingSymbol>FOCS</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001332638</rptOwnerCik>
            <rptOwnerName>STONE POINT CAPITAL LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>20 HORSENECK LANE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>GREENWICH</rptOwnerCity>
            <rptOwnerState>CT</rptOwnerState>
            <rptOwnerZipCode>06830-6327</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001748078</rptOwnerCik>
            <rptOwnerName>Trident FFP LP</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O STONE POINT CAPITAL LLC</rptOwnerStreet1>
            <rptOwnerStreet2>20 HORSENECK LANE</rptOwnerStreet2>
            <rptOwnerCity>GREENWICH</rptOwnerCity>
            <rptOwnerState>CT</rptOwnerState>
            <rptOwnerZipCode>06830-6327</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001593010</rptOwnerCik>
            <rptOwnerName>Trident VI, L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O STONE POINT CAPITAL LLC</rptOwnerStreet1>
            <rptOwnerStreet2>20 HORSENECK LANE</rptOwnerStreet2>
            <rptOwnerCity>GREENWICH</rptOwnerCity>
            <rptOwnerState>CT</rptOwnerState>
            <rptOwnerZipCode>06830-6327</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001593012</rptOwnerCik>
            <rptOwnerName>Trident VI Parallel Fund, L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O STONE POINT CAPITAL LLC</rptOwnerStreet1>
            <rptOwnerStreet2>20 HORSENECK LANE</rptOwnerStreet2>
            <rptOwnerCity>GREENWICH</rptOwnerCity>
            <rptOwnerState>CT</rptOwnerState>
            <rptOwnerZipCode>06830-6327</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001598644</rptOwnerCik>
            <rptOwnerName>Trident VI DE Parallel Fund, L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O STONE POINT CAPITAL LLC</rptOwnerStreet1>
            <rptOwnerStreet2>20 HORSENECK LANE</rptOwnerStreet2>
            <rptOwnerCity>GREENWICH</rptOwnerCity>
            <rptOwnerState>CT</rptOwnerState>
            <rptOwnerZipCode>06830-6327</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001748012</rptOwnerCik>
            <rptOwnerName>Trident FFP GP LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O STONE POINT CAPITAL LLC</rptOwnerStreet1>
            <rptOwnerStreet2>20 HORSENECK LANE</rptOwnerStreet2>
            <rptOwnerCity>GREENWICH</rptOwnerCity>
            <rptOwnerState>CT</rptOwnerState>
            <rptOwnerZipCode>06830-6327</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001690519</rptOwnerCik>
            <rptOwnerName>Trident Capital VI, L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O STONE POINT CAPITAL LLC</rptOwnerStreet1>
            <rptOwnerStreet2>20 HORSENECK LANE</rptOwnerStreet2>
            <rptOwnerCity>GREENWICH</rptOwnerCity>
            <rptOwnerState>CT</rptOwnerState>
            <rptOwnerZipCode>06830-6327</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class A Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2021-03-02</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>C</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1296885</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2396693</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnotes</value>
                    <footnoteId id="F3"/>
                    <footnoteId id="F8"/>
                    <footnoteId id="F11"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class A Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2021-03-02</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>2396693</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>46.20</value>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnotes</value>
                    <footnoteId id="F3"/>
                    <footnoteId id="F8"/>
                    <footnoteId id="F11"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class A Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2021-03-02</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>277650</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>46.20</value>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>996443</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnotes</value>
                    <footnoteId id="F4"/>
                    <footnoteId id="F9"/>
                    <footnoteId id="F10"/>
                    <footnoteId id="F11"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class A Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2021-03-02</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1946670</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>46.20</value>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>6986311</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnotes</value>
                    <footnoteId id="F5"/>
                    <footnoteId id="F9"/>
                    <footnoteId id="F10"/>
                    <footnoteId id="F11"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class A Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2021-03-02</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>41257</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>46.20</value>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>148062</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnotes</value>
                    <footnoteId id="F6"/>
                    <footnoteId id="F9"/>
                    <footnoteId id="F10"/>
                    <footnoteId id="F11"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Units of Focus Financial Partners, LLC</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2021-03-02</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>C</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1296885</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.00</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F1"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Class A Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>1296885</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>8601385</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnotes</value>
                    <footnoteId id="F7"/>
                    <footnoteId id="F8"/>
                    <footnoteId id="F11"/>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Units of Focus Financial Partners, LLC represent limited liability company units of Focus Financial Partners, LLC and an equal number of shares of Class B common stock (&quot;Class B Common Stock&quot;) of Focus Financial Partners Inc. (the &quot;Issuer&quot;), which together are exchangeable, at the option of Focus Financial Partners, LLC or the Issuer, on a one-for-one basis for (i) a share of Class A Common Stock (&quot;Class A Common Stock&quot;) of the Issuer, subject to conversion rate adjustments for stock splits, stock dividends, reclassification and other similar transactions or (ii) an equivalent amount of cash pursuant to the Fourth Amended and Restated Limited Liability Company Agreement of Focus Financial Partners, LLC.</footnote>
        <footnote id="F2">This amount represents the $48.00 secondary public offering price per share of Class A Common Stock less the underwriting discount of $1.80 per share of Class A Common Stock.</footnote>
        <footnote id="F3">These shares of Class A Common Stock are held by Trident FFP LP.</footnote>
        <footnote id="F4">These shares of Class A Common Stock are held by Trident VI, L.P.</footnote>
        <footnote id="F5">These shares of Class A Common Stock are held by Trident VI Parallel Fund, L.P.</footnote>
        <footnote id="F6">These shares of Class A Common Stock are held by Trident VI DE Parallel Fund, L.P.</footnote>
        <footnote id="F7">Held by Trident FFP LP.</footnote>
        <footnote id="F8">The sole general partner of Trident FFP LP is Trident FFP GP LLC.</footnote>
        <footnote id="F9">The sole general partner of each of Trident VI, L.P., Trident VI Parallel Fund, L.P. and Trident VI DE Parallel Fund, L.P. (collectively, the &quot;Trident VI Partnerships&quot;) is Trident Capital VI, L.P.</footnote>
        <footnote id="F10">Pursuant to certain management agreements, Stone Point Capital LLC has received delegated authority by Trident Capital VI, L.P. relating to the Trident VI Partnerships, provided that the delegated discretion to exercise voting rights may not be exercised on behalf of any of the Trident VI Partnerships without first receiving direction from the Investment Committee of Trident Capital VI, L.P. or a majority of the general partners of Trident Capital VI, L.P. The management agreements do not delegate any power with respect to the disposition of Class A Common Stock or Class B Common Stock held by the Trident VI Partnerships.</footnote>
        <footnote id="F11">Each of the Reporting Persons disclaims beneficial ownership of the securities reported herein, except to the extent of such Reporting Person's pecuniary interest therein. The filing of this statement shall not be deemed to be an admission that, for purposes of Section 16 of the Securities Exchange Act of 1934 or otherwise, the Reporting Persons are the beneficial owners of any securities reported herein.</footnote>
    </footnotes>

    <remarks>James D. Carey, a member and managing director of Stone Point Capital LLC, is a member of the board of directors of the Issuer. Mr. Carey is (i) an owner of one of the five general partners of Trident Capital VI, L.P. (the general partner of each of the Trident Partnerships) and (ii) an owner of one of five members of Trident FFP FP LLC (the general partner of Trident FFP LP). On the basis of the relationships between Mr. Carey and the Reporting Persons, each of the Reporting Persons may be deemed a director by deputization in respect of the Issuer.</remarks>

    <ownerSignature>
        <signatureName>TRIDENT FFP LP, By: Trident FFP GP LLC, its general partner, By: Trident VI, L.P., its sole member, By: Trident Capital VI, L.P. its general partner, By: DW Trident VI, LLC, its general partner, By: /s/ Jacqueline Giammarco, Name: Jacqueline Giammarco, Ti</signatureName>
        <signatureDate>2021-03-04</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>TRIDENT VI, L.P., By: Stone Point Capital LLC, its manager, By: /s/ Jacqueline Giammarco, Name: Jacqueline Giammarco, Title: Chief Compliance Officer</signatureName>
        <signatureDate>2021-03-04</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>TRIDENT VI PARALLEL FUND, L.P., By: Stone Point Capital LLC, its manager, By: /s/ Jacqueline Giammarco, Name: Jacqueline Giammarco, Title: Chief Compliance Officer</signatureName>
        <signatureDate>2021-03-04</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>TRIDENT VI DE PARALLEL FUND, L.P., By: Stone Point Capital LLC, its manager, By: /s/ Jacqueline Giammarco, Name: Jacqueline Giammarco, Title: Chief Compliance Officer</signatureName>
        <signatureDate>2021-03-04</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>TRIDENT FFP GP LLC, By: Trident VI, L.P., its sole member, By: Trident Capital VI, L.P. its general partner, By: DW Trident VI, LLC, its general partner, By: /s/ Jacqueline Giammarco, Name: Jacqueline Giammarco, Title: Vice President</signatureName>
        <signatureDate>2021-03-04</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>TRIDENT CAPITAL VI, L.P., By: DW Trident VI, LLC, a general partner, By: /s/ Jacqueline Giammarco, Name: Jacqueline Giammarco, Title: Vice President</signatureName>
        <signatureDate>2021-03-04</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>STONE POINT CAPITAL LLC, By: /s/ Jacqueline Giammarco, Name: Jacqueline Giammarco, Title: Chief Compliance Officer</signatureName>
        <signatureDate>2021-03-04</signatureDate>
    </ownerSignature>
</ownershipDocument>
