-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
 MFgwCgYEVQgBAQICAf8DSgAwRwJAW2sNKK9AVtBzYZmr6aGjlWyK3XmZv3dTINen
 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 WuD0NUmpb4Kfi+pJS26scnnpYm5dRsOR8nDabQY6JfqQGEiIEtIFiVlo4LTxQech
 qi7Of5MPdA0hQ+GcXINKaA==

<SEC-DOCUMENT>0001123292-05-000847.txt : 20051109
<SEC-HEADER>0001123292-05-000847.hdr.sgml : 20051109
<ACCEPTANCE-DATETIME>20051109182654
ACCESSION NUMBER:		0001123292-05-000847
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20051108
FILED AS OF DATE:		20051109
DATE AS OF CHANGE:		20051109

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			MAHAN JAMES S III
		CENTRAL INDEX KEY:			0001036743

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-24931
		FILM NUMBER:		051191516

	BUSINESS ADDRESS:	
		BUSINESS PHONE:		4048126710

	MAIL ADDRESS:	
		STREET 1:		3390 PEACHTREE RD NE
		STREET 2:		STE 1700
		CITY:			ATLANTA
		STATE:			GA
		ZIP:			30324

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			S1 CORP /DE/
		CENTRAL INDEX KEY:			0001063254
		STANDARD INDUSTRIAL CLASSIFICATION:	SERVICES-COMPUTER PROGRAMMING, DATA PROCESSING, ETC. [7370]
		IRS NUMBER:				582395199
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		3500 LENOX ROAD
		STREET 2:		SUITE 200
		CITY:			ATLANTA
		STATE:			GA
		ZIP:			30326
		BUSINESS PHONE:		4049233500

	MAIL ADDRESS:	
		STREET 1:		3500 LENOX ROAD
		STREET 2:		SUITE 200
		CITY:			ATLANTA
		STATE:			GA
		ZIP:			30326

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	SECURITY FIRST TECHNOLOGIES CORP
		DATE OF NAME CHANGE:	19980603
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2005-11-08</periodOfReport>

    <issuer>
        <issuerCik>0001063254</issuerCik>
        <issuerName>S1 CORP /DE/</issuerName>
        <issuerTradingSymbol>SONE</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001036743</rptOwnerCik>
            <rptOwnerName>MAHAN JAMES S III</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O S1 CORPORATION</rptOwnerStreet1>
            <rptOwnerStreet2>3500 LENOX ROAD</rptOwnerStreet2>
            <rptOwnerCity>ATLANTA</rptOwnerCity>
            <rptOwnerState>GA</rptOwnerState>
            <rptOwnerZipCode>30326</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>CEO and Chairman</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Employee Stock Option (right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>4.15</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2005-11-08</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>400000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2015-11-08</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>400000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>400000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The option vests with respect to 200,000 shares in four equal annual installments beginning on November 8, 2006, with respect to 100,000 shares if and when the market price of the Issuer's common stock reaches $8.00 per share, and with respect to the remaining 100,000 shares if and when the market price of the Issuer's common stock reaches $10.00 per share.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ R. Daniel Keating, Attorney-in-Fact</signatureName>
        <signatureDate>2005-11-09</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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