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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
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<SEC-DOCUMENT>0001218478-03-000002.txt : 20031024
<SEC-HEADER>0001218478-03-000002.hdr.sgml : 20031024
<ACCEPTANCE-DATETIME>20031024160045
ACCESSION NUMBER:		0001218478-03-000002
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20031023
FILED AS OF DATE:		20031024

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			SIEBEL SYSTEMS INC
		CENTRAL INDEX KEY:			0001006835
		STANDARD INDUSTRIAL CLASSIFICATION:	SERVICES-PREPACKAGED SOFTWARE [7372]
		IRS NUMBER:				943187233
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		2207 BRIDGEPOINTE PARKWAY
		CITY:			SAN MATEO
		STATE:			CA
		ZIP:			94404
		BUSINESS PHONE:		6504775000

	MAIL ADDRESS:	
		STREET 1:		2207 BRIDGEPOINTE PARKWAY
		CITY:			SAN MATEO
		STATE:			CA
		ZIP:			94404

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			HANSON MARK D
		CENTRAL INDEX KEY:			0001218478

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-20725
		FILM NUMBER:		03956571

	BUSINESS ADDRESS:	
		STREET 1:		C/O SIEBEL SYSTEMS INC
		STREET 2:		2207 BRIDGEPOINTE PARKWAY
		CITY:			SAN MATEO
		STATE:			CA
		ZIP:			94404
		BUSINESS PHONE:		6504775000

	MAIL ADDRESS:	
		STREET 1:		C/O SIEBEL SYSTEMS INC
		STREET 2:		2207 BRIDGEPOINTE PARKWAY
		CITY:			SAN MATEO
		STATE:			CA
		ZIP:			94404
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>c0001218478d20031024f4f.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<ownershipDocument><schemaVersion>X0201</schemaVersion>    <documentType>4</documentType><periodOfReport>2003-10-23</periodOfReport><notSubjectToSection16>0</notSubjectToSection16><issuer><issuerCik>0001006835</issuerCik><issuerName>SIEBEL SYSTEMS INC</issuerName>        <issuerTradingSymbol>SEBL</issuerTradingSymbol></issuer><reportingOwner><reportingOwnerId><rptOwnerCik>0001218478</rptOwnerCik><rptOwnerName>HANSON MARK D</rptOwnerName></reportingOwnerId><reportingOwnerAddress><rptOwnerStreet1>C/O SIEBEL SYSTEMS, INC.</rptOwnerStreet1><rptOwnerStreet2>2207 BRIDGEPOINTE PARKWAY</rptOwnerStreet2><rptOwnerCity>SAN MATEO</rptOwnerCity><rptOwnerState>CA</rptOwnerState><rptOwnerZipCode>94404</rptOwnerZipCode><rptOwnerStateDescription></rptOwnerStateDescription></reportingOwnerAddress><reportingOwnerRelationship><isDirector>0</isDirector><isOfficer>1</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther><officerTitle>Senior Vice President</officerTitle><otherText></otherText></reportingOwnerRelati
onship></reportingOwner><nonDerivativeTable><nonDerivativeTransaction><securityTitle><value>Common Stock</value></securityTitle><transactionDate><value>2003-10-23</value></transactionDate><deemedExecutionDate></deemedExecutionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>M</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionTimeliness><value></value></transactionTimeliness><transactionAmounts><transactionShares><value>25000</value></transactionShares><transactionPricePerShare><value>6.125</value></transactionPricePerShare><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>45496</value><footnoteId id="F1"/></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNat
ure></nonDerivativeTransaction><nonDerivativeTransaction><securityTitle><value>Common Stock</value></securityTitle><transactionDate><value>2003-10-23</value></transactionDate><deemedExecutionDate></deemedExecutionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>S</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionTimeliness><value></value></transactionTimeliness><transactionAmounts><transactionShares><value>25000</value></transactionShares><transactionPricePerShare><value>11.7883</value></transactionPricePerShare><transactionAcquiredDisposedCode><value>D</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>20496</value><footnoteId id="F1"/></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></nonDe
rivativeTransaction></nonDerivativeTable><derivativeTable><derivativeTransaction><securityTitle><value>Stock Options (Right to buy)</value></securityTitle><conversionOrExercisePrice><value>6.125</value></conversionOrExercisePrice><transactionDate><value>2003-10-23</value></transactionDate><deemedExecutionDate></deemedExecutionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>M</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>25000</value></transactionShares><transactionPricePerShare><value>6.125</value></transactionPricePerShare><transactionAcquiredDisposedCode><value>D</value></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><value>1999-12-15</value><footnoteId id="F2"/></exerciseDate><expirationDate><value>2008-12-25</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>25000</va
lue></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>175000</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></derivativeTransaction></derivativeTable><footnotes><footnote id="F1">Securities beneficailly owned includes 1,307 shares purchased under the Siebel Systems, Inc. Employee Stock Purchase Plan on June 30, 2003.</footnote><footnote id="F2">The option becomes exercisable as to 20% on December 15, 1999 and as to 5% each quarter thereafter.</footnote></footnotes><ownerSignature><signatureName>Mark D Hanson</signatureName><signatureDate>2003-10-24</signatureDate></ownerSignature></ownershipDocument>

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</SEC-DOCUMENT>
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