As filed with the Securities and Exchange Commission on March 30, 2011

Registration No. 333-171700

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

Amendment No. 3
to
FORM S-1
REGISTRATION STATEMENT
UNDER
THE SECURITIES ACT OF 1933

Kosmos Energy Ltd.
(Exact name of registrant as specified in its charter)

Clarendon House
2 Church Street
Hamilton HM 11, Bermuda
(441) 295-5950
(Address, including zip code, and telephone number, including area code, of registrant's principal executive offices)

Brian F. Maxted, Chief Executive Officer
c/o Kosmos Energy, LLC
8176 Park Lane, Suite 500
Dallas, TX 75231
(214) 445-9600
(Name, address, including zip code, and telephone number, including area code, of agent for service)

Approximate date of commencement of proposed sale to the public:
As soon as practicable after the effective date of this registration statement.

         If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, check the following box.    o

         If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.    o

         If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.    o

         If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.    o

         Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See the definitions of "large accelerated filer," "accelerated filer" and "smaller reporting company" in Rule 12b-2 of the Exchange Act.

         The registrant hereby amends this registration statement on such date or dates as may be necessary to delay its effective date until the registrant shall file a further amendment which specifically states that this registration statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933 or until the registration statement shall become effective on such date as the Commission, acting pursuant to said Section 8(a), may determine.

EXPLANATORY NOTE

        This Amendment No. 3 to the Registration Statement on Form S-1 (Registration No. 333-171700) is being filed in order to file certain exhibits. This Amendment No. 3 modifies the Index to Exhibits of the Registration Statement. The provisions of the Prospectus contained in Part 1 of Amendment No. 2 to the Registration on Form S-1 (Registration No. 333-171700) filed on March 23, 2011 are incorporated by reference in their entirety.

PART II

INFORMATION NOT REQUIRED IN PROSPECTUS

Item 13.    Other Expenses of Issuance and Distribution.

        The following table sets forth an itemization of the various costs and expenses, all of which we will pay, in connection with the issuance and distribution of the securities being registered. All of the amounts shown are estimated except the SEC registration fee, the NYSE listing fee and the FINRA filing fee:

Item 14.    Indemnification of Directors and Officers.

        Section 98 of the Companies Act 1981 of Bermuda (the "Bermuda Companies Act") provides generally that a Bermuda company may indemnify its directors, officers and auditors against any liability which by virtue of any rule of law would otherwise be imposed on them in respect of any negligence, default, breach of duty or breach of trust, except in cases where such liability arises from fraud or dishonesty of which such director, officer or auditor may be guilty in relation to the company. Section 98 further provides that a Bermuda company may indemnify its directors, officers and auditors against any liability incurred by them in defending any proceedings, whether civil or criminal, in which judgment is awarded in their favour or in which they are acquitted or granted relief by the Supreme Court of Bermuda pursuant to section 281 of the Bermuda Companies Act.

        We have adopted provisions in our bye-laws that provide that we shall indemnify our officers and directors in respect of their actions and omissions, except in respect of their fraud or dishonesty. Our bye-laws provide that the shareholders waive all claims or rights of action that they might have, individually or in right of the company, against any of the company's directors or officers for any act or failure to act in the performance of such director's or officer's duties, except in respect of any fraud or dishonesty of such director or officer. Section 98A of the Bermuda Companies Act permits us to purchase and maintain insurance for the benefit of any officer or director in respect of any loss or liability attaching to him in respect of any negligence, default, breach of duty or breach of trust, whether or not we may otherwise indemnify such officer or director.

        Insofar as indemnification by us for liabilities arising under the Securities Act may be permitted to our directors, officers or persons controlling the company pursuant to provisions of our bye-laws, or otherwise, we have been advised that in the opinion of the SEC, such indemnification is against public

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policy as expressed in the Securities Act and is therefore unenforceable. In the event that a claim for indemnification by such director, officer or controlling person of us in the successful defense of any action, suit or proceeding is asserted by such director, officer or controlling person in connection with the securities being offered, we will, unless in the opinion of our counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification by us is against public policy as expressed in the Securities Act and will be governed by the final adjudication of such issue.

        At the present time, there is no pending litigation or proceeding involving a director, officer, employee or other agent of ours in which indemnification would be required or permitted. We are not aware of any threatened litigation or proceeding, which may result in a claim for such indemnification.

        We carry insurance policies insuring our directors and officers against certain liabilities that they may incur in their capacity as directors and officers. In addition, we expect to enter into indemnification agreements with each of our directors prior to completion of the offering.

        Additionally, reference is made to the Underwriting Agreement filed as Exhibit 1.1. hereto, which provides for indemnification by the underwriters of Kosmos Energy Ltd., our directors and officers who sign the registration statement and persons who control Kosmos Energy Ltd., under certain circumstances.

Item 15.    Recent Sales of Unregistered Securities.

        During the past three years, Kosmos Energy Ltd.'s predecessor, Kosmos Energy Holdings, issued unregistered securities to funds affiliated with Warburg Pincus LLC ("Warburg Pincus"), The Blackstone Group L.P. ("Blackstone"), certain members of management, accredited employee investors and directors, as described below. None of these transactions involved any underwriters or any public offerings, and we believe that each of these transactions was exempt from the registration requirements pursuant to Section 3(a)(9) or Section 4(2) of the Securities Act of 1933, as amended. The recipients of the securities in these transactions represented their intention to acquire the securities for investment only and not with a view to or for sale in connection with any distribution thereof. The information presented below does not give effect to our corporate reorganization as described in the prospectus.

        During the fiscal year ended December 31, 2008, Kosmos Energy Holdings issued the following unregistered securities for the consideration listed:

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(1)

Kosmos Energy Holdings' financial statements reflect that the proceeds from the Series C funding were allocated on a relative fair value basis between the Series C Convertible Preferred Units and the C1 Common Units.

*

To be filed by amendment.

**

Filed as part of this registration statement on Form S-1 (Registration No. 333-171700) on January 14, 2011.

***

Filed as part of this registration statement on Form S-1 (Registration No. 333-171700) on March 3, 2011.

****

Filed as part of this registration statement on Form S-1 (Registration No. 333-171700) on March 23, 2011.

†

Management contract or compensatory plan or arrangement.

*

To be filed by amendment.

**

Filed as part of this registration statement on Form S-1 (Registration No. 333-171700) on January 14, 2011.

***

Filed as part of this registration statement on Form S-1 (Registration No. 333-171700) on March 3, 2011.

****

Filed as part of this registration statement on Form S-1 (Registration No. 333-171700) on March 23, 2011.

†

Management contract or compensatory plan or arrangement.