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 *
  WARBURG PINCUS & CO
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)
450 LEXINGTON AVENUE, NEW YORK
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)

NY, NY 100173147
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 42,477,931 $ (1) D (2)  
Series B Convertible Preferred Units   (1)   (1) Common Shares 28,664,667 $ (1) D (2)  
Series C Convertible Preferred Units   (1)   (1) Common Shares 1,254,447 $ (1) D (2)  
C1 Units   (1)   (1) Common Shares 2,372,092 $ (1) D (2)  
Series A Convertible Preferred Units   (1)   (1) Common Shares 42,014,200 $ (1) D (3)  
Series B Convertible Preferred Units   (1)   (1) Common Shares 28,351,734 $ (1) D (3)  
Series C Convertible Preferred Units   (1)   (1) Common Shares 1,240,739 $ (1) D (3)  
C1 Units   (1)   (1) Common Shares 2,418,984 $ (1) D (3)  
Series A Convertible Preferred Units   (1)   (1) Common Shares 87,664,716 $ (1) I See Footnote (4)
Series B Convertible Preferred Units   (1)   (1) Common Shares 59,157,300 $ (1) I See Footnote (4)
Series C Convertible Preferred Units   (1)   (1) Common Shares 2,588,876 $ (1) I See Footnote (4)
C1 Units   (1)   (1) Common Shares 4,968,245 $ (1) I See Footnote (4)

Reporting Owners

Reporting Owner Name / Address Relationships
Director 10% Owner Officer Other
WARBURG PINCUS & CO
450 LEXINGTON AVENUE
NEW YORK
NY, NY 100173147
    X    
WARBURG PINCUS LLC
450 LEXINGTON AVENUE
NEW YORK, NY 10017
    X    
Warburg Pincus Partners LLC
450 LEXINGTON AVENUE
NEW YORK, NY 10017
    X    
WARBURG PINCUS PRIVATE EQUITY VIII L P
450 LEXINGTON AVENUE
NEW YORK, NY 10017
    X    
Warburg Pincus International Partners, L.P.
450 LEXINGTON AVENUE
NEW YORK, NY 10017
    X    
KAYE CHARLES R
C/O WARBURG PINCUS LLC
450 LEXINGTON AVE
NEW YORK, NY 10017
    X    
LANDY JOSEPH
C/O WARBURG PINCUS LLC
466 LEXINGTON AVE
NEW YORK, NY 10017
    X    

Signatures

/s/ Scott A. Arenare, Partner of Warburg Pincus & Co. 05/11/2011
**Signature of Reporting Person Date

/s/ Scott A. Arenare, Managing Director of Warburg Pincus LLC 05/11/2011
**Signature of Reporting Person Date

/s/ Scott A. Arenare, Partner of Warburg Pincus & Co., managing member of Warburg Pincus Partners, LLC 05/11/2011
**Signature of Reporting Person Date

/s/ Scott A. Arenare, Partner of Warburg Pincus & Co., managing member of Warburg Pincus Partners, LLC, general partner of Warburg Pincus Private Equity VIII, L.P. 05/11/2011
**Signature of Reporting Person Date

/s/ Scott A. Arenare, Partner of Warburg Pincus & Co., managing member of Warburg Pincus Partners, LLC, general partner of Warburg Pincus International Partners, L.P. 05/11/2011
**Signature of Reporting Person Date

/s/ Scott A. Arenare, as attorney-in-fact for Charles R. Kaye* 05/11/2011
**Signature of Reporting Person Date

/s/ Scott A. Arenare, as attorney-in-fact for Joseph R. Landy** 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 units.
(2) Pursuant to the Corporate Reorganization, Warburg Pincus Private Equity VIII, L.P., a Delaware limited partnership ("WPPE VIII"), has the right to acquire as of the date of this filing 74,769,137 Common Shares in connection with the Closing, which is expected to occur on May 16, 2011. Pursuant to the Corporate Reorganization, two affiliated limited partnerships of WPPE VIII (collectively, and together with WPPE VIII, "WP VIII") have the right to acquire as of the date of this filing 2,167,693 Common Shares and 216,337 Common Shares, respectively, in connection with the Closing.
(3) Pursuant to the Corporate Reorganization, Warburg Pincus International Partners, L.P., a Delaware limited partnership ("WPIP LP"), has the right to acquire as of the date of this filing 74,025,658 Common Shares in connection with the Closing. Pursuant to the Corporate Reorganization, two affiliated limited partnerships of WPIP LP (collectively, and together with WPIP LP, "WPIP") have the right to acquire as of the date of this filing 3,086,130 Common Shares and 114,183 Common Shares, respectively, in connection with the Closing.
(4) Warburg Pincus Partners, LLC, a New York limited liability company ("WP Partners") and direct subsidiary of Warburg Pincus & Co., a New York general partnership ("WP"), is the sole general partner of WPPE VIII and WPIP LP. WP is the managing member of WP Partners. WP VIII and WPIP are managed by Warburg Pincus LLC, a New York limited liability company ("WP LLC"). Charles R. Kaye and Joseph P. Landy are Managing General Partners of WP and Managing Members and Co-Presidents of WP LLC. Pursuant to Rule 16a-1 of the Securities Exchange Act of 1934, as amended, WP, WP Partners, WP LLC, Mr. Kaye and Mr. Landy may be deemed to be the beneficial owners of any securities reported herein that may be deemed to be beneficially owned by WP VIII or WPIP. Each of WP VIII, WPIP, WP, WP Partners, WP LLC, Mr. Kaye and Mr. Landy disclaims beneficial ownership with respect to any Common Shares in which they do not have a direct pecuniary interest.
 
Remarks:
* - Power of Attorney given by Mr. Kaye was previously filed with the U.S. Securities and Exchange Commission ("SEC") on March 2, 2006 as an exhibit to the Schedule 13D filed by Building Products, LLC with respect to Builders FirstSource, Inc.
** - Power of Attorney given by Mr. Landy was previously filed with the SEC on March 2, 2006 as an exhibit to the Schedule 13D filed by Building Products, LLC with respect to Builders FirstSource, Inc.

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