<PAGE>
    AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON NOVEMBER 14, 2005

                                                           REGISTRATION NO. 333-
================================================================================

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

                               ------------------
                                    FORM S-8

                        REGISTRATION STATEMENT UNDER THE
                             SECURITIES ACT OF 1933

                               ------------------

                            CENTURY ALUMINUM COMPANY
             (EXACT NAME OF REGISTRANT AS SPECIFIED IN ITS CHARTER)

         DELAWARE                                       13-3070826
(State or other jurisdiction of             (I.R.S. Employer Identification No.)
incorporation or organization)

            2511 GARDEN ROAD                                93940
          BUILDING A, SUITE 200                          (Zip code)
          MONTEREY, CALIFORNIA
(Address of principal executive offices)

                             ----------------------

                          CENTURY ALUMINUM 401(K) PLAN
                            (FULL TITLE OF THE PLAN)

                                GERALD J. KITCHEN
                   EXECUTIVE VICE PRESIDENT, GENERAL COUNSEL,
                   CHIEF ADMINISTRATIVE OFFICER AND SECRETARY
                            CENTURY ALUMINUM COMPANY
                                2511 GARDEN ROAD
                              BUILDING A, SUITE 200
                           MONTEREY, CALIFORNIA 93940
                                 (831) 642-8300
 (NAME, ADDRESS AND TELEPHONE NUMBER, INCLUDING AREA CODE, OF AGENT FOR SERVICE)

                        -------------------------------

                         CALCULATION OF REGISTRATION FEE

<TABLE>
<CAPTION>
===========================================================================================================
                                                         Proposed         Proposed
                                                         maximum          maximum
  Title of securities to be         Amount to be      offering price      aggregate            Amount of
         registered                  registered       per share(1)     offering price(1)   registration fee
-------------------------------   -----------------   --------------   -----------------   ----------------
<S>                               <C>                 <C>              <C>                 <C>
Common Stock, $.01 par value...   200,000 Shares(2)   $        19.25   $        3,850,000  $         453.15
===========================================================================================================
</TABLE>

(1)   Estimated solely for the purpose of computing the registration fee
      pursuant to Rule 457, based on the average of the high and low prices for
      the Common Stock as reported on the Nasdaq National Market System on
      November 7, 2005.

(2)   In addition, pursuant to Rule 416(c) under the Securities Act of 1933,
      this registration statement also covers an indeterminate amount of
      interests to be offered or sold pursuant to the employee benefit plan(s)
      described herein.

================================================================================

<PAGE>

                           INCORPORATION BY REFERENCE

      This Registration Statement on Form S-8 relates to the registration of
additional shares and plan interests under the Century Aluminum 401(k) Plan
(formerly, the Ravenswood Aluminum Corporation Salaried Employee Defined
Contribution Retirement Plan; the "Plan"). Pursuant to General Instruction E of
Form S-8, the contents of the Registration Statement on Form S-8 (Registration
No. 333-07239) filed with the Securities and Exchange Commission on June 28,
1996 are incorporated by reference herein. This Registration Statement also
incorporates by reference the Plan's latest annual report filed pursuant to
Section 15(d) of the Exchange Act and all future annual reports filed by the
Plan prior to the filing of a post-effective amendment which indicates that all
securities offered have been sold or which deregisters all securities then
remaining unsold.

                                      -2-
<PAGE>

                                   SIGNATURES

      THE REGISTRANT. Pursuant to the requirements of the Securities Act of
1933, the registrant certifies that it has reasonable grounds to believe that it
meets all of the requirements for filing on Form S-8 and has duly caused this
registration statement to be signed on its behalf by the undersigned, thereunto
duly authorized, in the City of Monterey, State of California, on the 14th day
of November, 2005.

                                         CENTURY ALUMINUM COMPANY

                                         By: /s/ David W. Beckley
                                             -----------------------------------
                                             Name:  David W. Beckley
                                             Title: Executive Vice President and
                                                    Chief Financial Officer

      Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed by the following persons in the
capacities and on the dates indicated.

<TABLE>
<CAPTION>
            SIGNATURE                                  TITLE                            DATE
-------------------------------------   --------------------------------------   -----------------
<S>                                     <C>                                      <C>
                                         Chairman and Chief Executive Officer
/s/ Craig A. Davis                           (Principal Executive Officer)       November 14, 2005
-----------------------------
Craig A. Davis
                                             Executive Vice President and
                                          Chief Financial Officer (Principal
/s/ David W. Beckley                       Financial Officer and Principal
-----------------------------                   Accounting Officer)              November 14, 2005
David W. Beckley

              *                                      Director                    November 14, 2005
-----------------------------
Roman A. Bninski

              *                                      Director                    November 14, 2005
-----------------------------
Robert E. Fishman

              *                                      Director                    November 14, 2005
-----------------------------
John C. Fontaine

              *                                      Director                    November 14, 2005
-----------------------------
John P. O'Brien

              *                                      Director                    November 14, 2005
-----------------------------
Stuart M. Schreiber

              *                                      Director                    November 14, 2005
-----------------------------
Jack E. Thompson
</TABLE>

                                       -3-
<PAGE>

<TABLE>
<CAPTION>
            SIGNATURE                                  TITLE                            DATE
-------------------------------------   --------------------------------------   -----------------
<S>                                     <C>                                      <C>
              *                                      Director                    November 14, 2005
-----------------------------
Willy R. Strothotte

* By:    /s/ Peter C. McGuire
  -----------------------------------
Peter C. McGuire, as Attorney-in-Fact
</TABLE>

                                      -4-
<PAGE>

      THE PLAN. Pursuant to the requirements of the Securities Act of 1933, the
Plan administrator has duly caused this registration statement to be signed on
its behalf by the undersigned, thereunto duly authorized, in the City of
Monterey, State of California, on the 14th day of November, 2005.

                                          CENTURY ALUMINUM 401(K) PLAN

                                          By: Retirement Committee of Century
                                                Aluminum 401(k) Plan

                                          By: /s/ David W. Beckley
                                              ----------------------------------
                                              Name:  David W. Beckley
                                              Title: Member

                                      -5-
<PAGE>

                                INDEX TO EXHIBITS

<TABLE>
<CAPTION>
Exhibit No.                                Description of Exhibit
----------    ---------------------------------------------------------------------------------------------
<S>           <C>
5.1           Internal Revenue Service determination letter that the Plan is qualified under Section 401(k)
              of the Internal Revenue Code.

23.1          Consent of Deloitte & Touche LLP.

24.1          Powers of Attorney
</TABLE>

                                      -6-
[{"type": "S-8", "sequence": "1", "filename": "y14765csv8.txt", "description": "FORM S-8", "secsgml_size_bytes": 9358}]
{"company-data": {"conformed-name": "CENTURY ALUMINUM CO", "cik": "0000949157", "assigned-sic": "3334", "irs-number": "133070826", "state-of-incorporation": "DE", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-129699", "film-number": "051204380"}, "business-address": {"street1": "2511 GARDEN ROAD", "street2": "BUILDING A SUITE 200", "city": "MONTEREY", "state": "CA", "zip": "93940", "phone": "3042736000"}, "mail-address": {"street1": "2511 GARDEN ROAD", "street2": "BUILDING A SUITE 200", "city": "MONTEREY", "state": "CA", "zip": "93940"}}
AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON NOVEMBER 14, 2005

                                                           REGISTRATION NO. 333-
================================================================================

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

                               ------------------
                                    FORM S-8

                        REGISTRATION STATEMENT UNDER THE
                             SECURITIES ACT OF 1933

                               ------------------

                            CENTURY ALUMINUM COMPANY
             (EXACT NAME OF REGISTRANT AS SPECIFIED IN ITS CHARTER)

         DELAWARE                                       13-3070826
(State or other jurisdiction of             (I.R.S. Employer Identification No.)
incorporation or organization)

            2511 GARDEN ROAD                                93940
          BUILDING A, SUITE 200                          (Zip code)
          MONTEREY, CALIFORNIA
(Address of principal executive offices)

                             ----------------------

                          CENTURY ALUMINUM 401(K) PLAN
                            (FULL TITLE OF THE PLAN)

                                GERALD J. KITCHEN
                   EXECUTIVE VICE PRESIDENT, GENERAL COUNSEL,
                   CHIEF ADMINISTRATIVE OFFICER AND SECRETARY
                            CENTURY ALUMINUM COMPANY
                                2511 GARDEN ROAD
                              BUILDING A, SUITE 200
                           MONTEREY, CALIFORNIA 93940
                                 (831) 642-8300
 (NAME, ADDRESS AND TELEPHONE NUMBER, INCLUDING AREA CODE, OF AGENT FOR SERVICE)

                        -------------------------------

                         CALCULATION OF REGISTRATION FEE
===========================================================================================================
                                                         Proposed         Proposed
                                                         maximum          maximum
  Title of securities to be         Amount to be      offering price      aggregate            Amount of
         registered                  registered       per share(1)     offering price(1)   registration fee
-------------------------------   -----------------   --------------   -----------------   ----------------
Common Stock, $.01 par value...   200,000 Shares(2)   $        19.25   $        3,850,000  $         453.15
===========================================================================================================
(1)   Estimated solely for the purpose of computing the registration fee
      pursuant to Rule 457, based on the average of the high and low prices for
      the Common Stock as reported on the Nasdaq National Market System on
      November 7, 2005.

(2)   In addition, pursuant to Rule 416(c) under the Securities Act of 1933,
      this registration statement also covers an indeterminate amount of
      interests to be offered or sold pursuant to the employee benefit plan(s)
      described herein.

================================================================================
INCORPORATION BY REFERENCE

      This Registration Statement on Form S-8 relates to the registration of
additional shares and plan interests under the Century Aluminum 401(k) Plan
(formerly, the Ravenswood Aluminum Corporation Salaried Employee Defined
Contribution Retirement Plan; the "Plan"). Pursuant to General Instruction E of
Form S-8, the contents of the Registration Statement on Form S-8 (Registration
No. 333-07239) filed with the Securities and Exchange Commission on June 28,
1996 are incorporated by reference herein. This Registration Statement also
incorporates by reference the Plan's latest annual report filed pursuant to
Section 15(d) of the Exchange Act and all future annual reports filed by the
Plan prior to the filing of a post-effective amendment which indicates that all
securities offered have been sold or which deregisters all securities then
remaining unsold.

                                      -2-
SIGNATURES

      THE REGISTRANT. Pursuant to the requirements of the Securities Act of
1933, the registrant certifies that it has reasonable grounds to believe that it
meets all of the requirements for filing on Form S-8 and has duly caused this
registration statement to be signed on its behalf by the undersigned, thereunto
duly authorized, in the City of Monterey, State of California, on the 14th day
of November, 2005.

                                         CENTURY ALUMINUM COMPANY

                                         By: /s/ David W. Beckley
                                             -----------------------------------
                                             Name:  David W. Beckley
                                             Title: Executive Vice President and
                                                    Chief Financial Officer

      Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed by the following persons in the
capacities and on the dates indicated.
SIGNATURE                                  TITLE                            DATE
-------------------------------------   --------------------------------------   -----------------
Chairman and Chief Executive Officer
/s/ Craig A. Davis                           (Principal Executive Officer)       November 14, 2005
-----------------------------
Craig A. Davis
                                             Executive Vice President and
                                          Chief Financial Officer (Principal
/s/ David W. Beckley                       Financial Officer and Principal
-----------------------------                   Accounting Officer)              November 14, 2005
David W. Beckley

              *                                      Director                    November 14, 2005
-----------------------------
Roman A. Bninski

              *                                      Director                    November 14, 2005
-----------------------------
Robert E. Fishman

              *                                      Director                    November 14, 2005
-----------------------------
John C. Fontaine

              *                                      Director                    November 14, 2005
-----------------------------
John P. O'Brien

              *                                      Director                    November 14, 2005
-----------------------------
Stuart M. Schreiber

              *                                      Director                    November 14, 2005
-----------------------------
Jack E. Thompson
-3-
SIGNATURE                                  TITLE                            DATE
-------------------------------------   --------------------------------------   -----------------
*                                      Director                    November 14, 2005
-----------------------------
Willy R. Strothotte

* By:    /s/ Peter C. McGuire
  -----------------------------------
Peter C. McGuire, as Attorney-in-Fact
-4-
THE PLAN. Pursuant to the requirements of the Securities Act of 1933, the
Plan administrator has duly caused this registration statement to be signed on
its behalf by the undersigned, thereunto duly authorized, in the City of
Monterey, State of California, on the 14th day of November, 2005.

                                          CENTURY ALUMINUM 401(K) PLAN

                                          By: Retirement Committee of Century
                                                Aluminum 401(k) Plan

                                          By: /s/ David W. Beckley
                                              ----------------------------------
                                              Name:  David W. Beckley
                                              Title: Member

                                      -5-
INDEX TO EXHIBITS
Exhibit No.                                Description of Exhibit
----------    ---------------------------------------------------------------------------------------------
5.1           Internal Revenue Service determination letter that the Plan is qualified under Section 401(k)
              of the Internal Revenue Code.

23.1          Consent of Deloitte & Touche LLP.

24.1          Powers of Attorney
-6-