As filed with the Securities and Exchange Commission on February 21, 2018

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

POST-EFFECTIVE AMENDMENT NO. 1

TO

FORM S-8

REGISTRATION STATEMENT NO. 333-217764

POST-EFFECTIVE AMENDMENT NO. 1

TO

FORM S-8

REGISTRATION STATEMENT NO. 333-212403

POST-EFFECTIVE AMENDMENT NO. 1

TO

FORM S-8

REGISTRATION STATEMENT NO. 333-211094

POST-EFFECTIVE AMENDMENT NO. 1

TO

FORM S-8

REGISTRATION STATEMENT NO. 333-203877

POST-EFFECTIVE AMENDMENT NO. 1

TO

FORM S-8

REGISTRATION STATEMENT NO. 333-164624

POST-EFFECTIVE AMENDMENT NO. 1

TO

FORM S-8

REGISTRATION STATEMENT NO. 333-163883

UNDER

THE SECURITIES ACT OF 1933

Cobalt International Energy, Inc.

(Exact Name of Registrant as Specified in Its Charter)

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 definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act.    ☐

DEREGISTRATION OF SECURITIES

This Post-Effective Amendment No. 1 filed by Cobalt International Energy, Inc., a Delaware corporation (the “Company”), deregisters all shares of common stock, par value $0.01, of the Company (the “Common Stock”) remaining unissued under the following Registration Statements on Form S-8 (the “Registration Statements”) filed by the Company with the Securities and Exchange Commission:

As previously disclosed, on December 14, 2017, the Company and certain of its affiliates filed voluntary petitions for relief (and the cases commenced thereby, the “Chapter 11 Cases”) under chapter 11 of the United States Bankruptcy Code in the United States Bankruptcy Court for the Southern District of Texas. The Chapter 11 Cases are being administered jointly under the caption In re Cobalt International Energy, Inc., et al. , Case No. 17-36709.

As a result of the Chapter 11 Cases, the Company has terminated all offerings of securities pursuant to the Registration Statements. In accordance with an undertaking made by the Company in the Registration Statements to remove from registration, by means of a post-effective amendment, any of the securities that had been registered for issuance that remain unsold at the termination of such offering, the Company hereby removes from registration by means of this Post-Effective Amendment No. 1 all of such securities registered but unsold under the Registration Statements. The Registration Statements are hereby amended, as appropriate, to reflect the deregistration of such securities and the Company hereby terminates the effectiveness of the Registration Statements.