Ownership Submission
FORM 3
UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940
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(Print or Type Responses)
1. Name and Address of Reporting Person *
  Blackstone Holdings III L.P.
2. Date of Event Requiring Statement (Month/Day/Year)
05/11/2011
3. Issuer Name and Ticker or Trading Symbol
Kosmos Energy Ltd. [KOS]
(Last)
(First)
(Middle)
C/O THE BLACKSTONE GROUP L.P., 345 PARK AVENUE
4. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
_____ Director __X__ 10% Owner
_____ Officer (give title below) _____ Other (specify below)
5. If Amendment, Date Original Filed(Month/Day/Year)
(Street)

NEW YORK, NY 10154
6. Individual or Joint/Group Filing(Check Applicable Line)
___ Form filed by One Reporting Person
_X_ Form filed by More than One Reporting Person
(City)
(State)
(Zip)
Table I - Non-Derivative Securities Beneficially Owned
1.Title of Security
(Instr. 4)
2. Amount of Securities Beneficially Owned
(Instr. 4)
3. Ownership Form: Direct (D) or Indirect (I)
(Instr. 5)
4. Nature of Indirect Beneficial Ownership
(Instr. 5)

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly. SEC 1473 (7-02)
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Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security
(Instr. 4)
2. Date Exercisable and Expiration Date
(Month/Day/Year)
3. Title and Amount of Securities Underlying Derivative Security
(Instr. 4)
4. Conversion or Exercise Price of Derivative Security 5. Ownership Form of Derivative Security: Direct (D) or Indirect (I)
(Instr. 5)
6. Nature of Indirect Beneficial Ownership
(Instr. 5)
Date Exercisable Expiration Date Title Amount or Number of Shares
Series A Convertible Preferred Units   (1)   (1) Common Shares 67,046,010 $ (1) I See Footnotes (2) (7) (8)
Series B Convertible Preferred Units   (1)   (1) Common Shares 45,478,980 $ (1) I See Footnotes (2) (7) (8)
Series C Convertible Preferred Units   (1)   (1) Common Shares 1,984,092 $ (1) I See Footnotes (2) (7) (8)
C1 Units   (1)   (1) Common Shares 3,807,630 $ (1) I See Footnotes (2) (7) (8)
Series A Convertible Preferred Units   (1)   (1) Common Shares 1,093,390 $ (1) I See Footnotes (3) (7) (8)
Series B Convertible Preferred Units   (1)   (1) Common Shares 741,674 $ (1) I See Footnotes (3) (7) (8)
Series C Convertible Preferred Units   (1)   (1) Common Shares 32,357 $ (1) I See Footnotes (3) (7) (8)
C1 Units   (1)   (1) Common Shares 62,094 $ (1) I See Footnotes (3) (7) (8)
Series A Convertible Preferred Units   (1)   (1) Common Shares 1,845,716 $ (1) I See Footnotes (4) (7) (8)
Series B Convertible Preferred Units   (1)   (1) Common Shares 1,122,345 $ (1) I See Footnotes (4) (7) (8)
Series C Convertible Preferred Units   (1)   (1) Common Shares 52,350 $ (1) I See Footnotes (4) (7) (8)
C1 Units   (1)   (1) Common Shares 100,460 $ (1) I See Footnotes (4) (7) (8)
Series A Convertible Preferred Units   (1)   (1) Common Shares 1,532,489 $ (1) I See Footnotes (5) (7) (8)
Series B Convertible Preferred Units   (1)   (1) Common Shares 931,875 $ (1) I See Footnotes (5) (7) (8)
Series C Convertible Preferred Units   (1)   (1) Common Shares 43,466 $ (1) I See Footnotes (5) (7) (8)
C1 Units   (1)   (1) Common Shares 83,413 $ (1) I See Footnotes (5) (7) (8)
Series A Convertible Preferred Units   (1)   (1) Common Shares 208,082 $ (1) I See Footnotes (6) (7) (8)
Series B Convertible Preferred Units   (1)   (1) Common Shares 126,533 $ (1) I See Footnotes (6) (7) (8)
Series C Convertible Preferred Units   (1)   (1) Common Shares 5,899 $ (1) I See Footnotes (6) (7) (8)
C1 Units   (1)   (1) Common Shares 11,325 $ (1) I See Footnotes (6) (7) (8)

Reporting Owners

Reporting Owner Name / Address Relationships
Director 10% Owner Officer Other
Blackstone Holdings III L.P.
C/O THE BLACKSTONE GROUP L.P.
345 PARK AVENUE
NEW YORK, NY 10154
    X    
BLACKSTONE MANAGEMENT ASSOCIATES CAYMAN IV LP
C/O THE BLACKSTONE GROUP L.P.
345 PARK AVENUE
NEW YORK, NY 10154
    X    
BLACKSTONE FAMILY GP LLC
C/O THE BLACKSTONE GROUP L.P.
345 PARK AVENUE
NEW YORK, NY 10154
    X    
Blackstone Holdings III GP L.P.
C/O THE BLACKSTONE GROUP L.P.
345 PARK AVENUE
NEW YORK, NY 10154
    X    
Blackstone Holdings III GP Management L.L.C.
C/O THE BLACKSTONE GROUP L.P.
345 PARK AVENUE
NEW YORK, NY 10154
    X    
Blackstone Group L.P.
C/O THE BLACKSTONE GROUP L.P.
345 PARK AVENUE
NEW YORK, NY 10154
    X    
Blackstone Group Management L.L.C.
C/O THE BLACKSTONE GROUP L.P.
345 PARK AVENUE
NEW YORK, NY 10154
    X    
SCHWARZMAN STEPHEN A
C/O THE BLACKSTONE GROUP L.P.
345 PARK AVENUE
NEW YORK, NY 10154
    X    

Signatures

/s/ Robert L. Friedman, Authorized Person, Blackstone Holdings III GP Management L.L.C., General Partner of Blackstone Holdings III GP L.P., General Partner of Blackstone Holdings III L.P. 05/11/2011
**Signature of Reporting Person Date

/s/ Robert L. Friedman, Senior Managing Director, BCP IV GP L.L.C., general partner of Blackstone Management Associates (Cayman) IV L.P. 05/11/2011
**Signature of Reporting Person Date

/s/ Robert L. Friedman, Senior Managing Director for Blackstone Family GP L.L.C. 05/11/2011
**Signature of Reporting Person Date

/s/ Robert L. Friedman, Authorized Person, Blackstone Holdings III GP Management L.L.C., General Partner of Blackstone Holdings III G.P. L.P. 05/11/2011
**Signature of Reporting Person Date

/s/ Robert L. Friedman, Authorized Person for Blackstone Holdings III GP Management L.L.C. 05/11/2011
**Signature of Reporting Person Date

/s/ Kathleen Skero, Managing Director, Principle Accounting Officer, and Assistant Secretary, Blackstone Group Management L.L.C., General Partner of The Blackstone Group L.P. 05/11/2011
**Signature of Reporting Person Date

/s/ Kathleen Skero, Managing Director, Principle Accounting Officer, and Assistant Secretary for Blackstone Group Management L.L.C. 05/11/2011
**Signature of Reporting Person Date

/s/ Stephen A, Schwarzman 05/11/2011
**Signature of Reporting Person Date

Explanation of Responses:

* If the form is filed by more than one reporting person, see Instruction 5(b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1) The securities underlying the derivative securities reported herein are issuable pursuant to the corporate reorganization (the "Corporate Reorganization") that will be completed simultaneously with, or prior to the closing (the "Closing") of the initial public offering of common shares, par value $0.01 (the "Common Shares") of Kosmos Energy Ltd., in exchange for the outstanding units of Kosmos Energy Holdings ("KEH"), which units are exchangeable pursuant to the Fourth Amended and Restated Operating Agreement of KEH upon the Closing based on the pre-offering equity value of such convertible preferred units.
(2) These securities are held by Blackstone Capital Partners (Cayman) IV L.P. ("BCP Cayman IV"). Pursuant to the Corporate Reorganization, BCP Cayman IV has the right to acquire as of the date of this filing 118,316,711 Common Shares in connection with the Closing, which is expected to occur on May 16, 2011.
(3) These securities are held by Blackstone Capital Partners (Cayman) IV-A L.P. ("BCP Cayman IV-A"). Pursuant to the Corporate Reorganization, BCP Cayman IV-A has the right to acquire as of the date of this filing 1,929,515 Common Shares in connection with the Closing, which is expected to occur on May 16, 2011.
(4) These securities are held by Blackstone Family Investment Partnership (Cayman) IV-A L.P. ("BFIP"). Pursuant to the Corporate Reorganization, BFIP has the right to acquire as of the date of this filing 3,120,870 Common Shares in connection with the Closing, which is expected to occur on May 16, 2011.
(5) These securities are held by Blackstone Family Investment Partnership (Cayman) IV-A SMD L.P. ("BFIP SMD"). Pursuant to the Corporate Reorganization, BFIP SMD has the right to acquire as of the date of this filing 2,591,243 Common Shares in connection with the Closing, which is expected to occur on May 16, 2011.
(6) These securities are held by Blackstone Participation Partnership (Cayman) IV L.P. ("BPP"). Pursuant to the Corporate Reorganization, BPP has the right to acquire as of the date of this filing 351,839 Common Shares in connection with the Closing, which is expected to occur on May 16, 2011.
(7) The general partner of BFIP SMD is Blackstone Family GP L.L.C. which is controlled by Mr. Stephen A. Schwarzman, its founder. The general partner of BCP Cayman IV and BCP Cayman IV-A is Blackstone Management Associates (Cayman) IV L.P. ("BMA"). A general partner of BMA, BFIP, and BPP is BCP IV GP L.L.C ("BCP IV"). Blackstone Holdings III L.P. is the sole member of BCP IV. The general partner of Blackstone Holdings III L.P. is Blackstone Holdings III GP L.P. The general partner of Blackstone Holdings III GP L.P. is Blackstone Holdings III GP Management L.L.C. The sole member of Blackstone Holdings III GP Management L.L.C. is The Blackstone Group L.P. The general partner of The Blackstone Group L.P. is Blackstone Group Management L.L.C. Blackstone Group Management L.L.C. is controlled by Mr. Stephen A. Schwarzman, its founder.
(8) 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.
 
Remarks:
Because no more than 10 reporting persons can file any one Form 3 through the Securities and Exchange Commission's EDGAR system, BCP IV GP L.L.C., Blackstone Capital Partners (Cayman) IV L.P., Blackstone Capital Partners (Cayman) IV-A L.P, Blackstone Family Investment Partnership (Cayman) IV-A L.P., Blackstone Family Investment Partnership (Cayman) IV-A SMD L.P., and Blackstone Participation Partnership (Cayman) IV L.P. have filed a separate Form 3.

Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, See Instruction 6 for procedure.

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