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                                                      Registration No. 333-57763


                       SECURITIES AND EXCHANGE COMMISSION

                             WASHINGTON, D.C. 20549

                          -----------------------------
                         Post Effective Amendment No. 1
                                       TO
                                    FORM S-4

                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

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

                          THE COLONIAL BANCGROUP, INC.

             (Exact name of Registrant as specified in its charter)

                                                       
       Delaware                         6711                              63-0661573
(State of Incorporation)    (Primary Standard Industrial     (I.R.S. Employer Identification No.)
                             Classification Code Number)



   One Commerce Street, Suite 800                               (334) 240-5000
      Montgomery, Alabama 36104                                 (Telephone No.)
(Address of principal executive offices)

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

                               William A. McCrary
                                    Secretary
                              Post Office Box 1108
                            Montgomery, Alabama 36101
                     (Name and address of agent for service)

                                   Copies to:

                                Willard H. Henson
                         Miller, Hamilton, Snider & Odom
                         One Commerce Street, Suite 305
                            Montgomery, Alabama 36104

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

         If the securities being registered on this Form are being offered in
connection with the formation of a holding company and there is compliance with
General Instruction G, check the following box. [ ]


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         The Colonial BancGroup, Inc. ("BancGroup") registered 2,800,002 shares
of its Common Stock on Form S-4, registration no. 333-57763, pursuant to the
acquisition of FirstBank, a Texas state bank. Such registration was declared
effective on July 14, 1998. After the Agreement and Plan of Merger between
FirstBank and BancGroup, dated as of May 5, 1998 (the "Merger Agreement") was
executed, and after the registration of the shares to be issued in the merger
was effective, BancGroup issued a 2 for 1 stock split, effected in the form of a
100% stock dividend (the "Stock Split"). The Merger Agreement provided that any
such stock split would result in a proportionate increase of BancGroup shares to
be issued pursuant to the merger. Pursuant to SEC Rule 416(b), the registration
statement is deemed to cover the additional shares resulting from the Stock
Split. Accordingly, the Form S-4, registration no. 333-57763, is deemed to
register a total of 5,600,004 shares of BancGroup common stock.

         A total of 2,782,038 shares were issued in the merger on August 31,
1998. Pursuant to the undertaking given by BancGroup in such registration
statement in accordance with Regulation S-K, item 512(a)(3), BancGroup hereby
removes 2,817,966 shares from registration, which represents the number of
shares registered less the number of shares issued in the merger.

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                                    SIGNATURE


         Pursuant to Regulation S-K, item 512(a)(3) and SEC Rule 478(a)(4), the
undersigned registrant hereby executes this post effective amendment to its
registration statement on Form S-4 to remove from registration certain shares
not issued and has caused this registration statement to be signed on its behalf
by the undersigned, thereunto duly authorized, in the City of Montgomery,
Alabama, on the 9th day of January, 2001.

                                    THE COLONIAL BANCGROUP, INC.


                                    By: /s/ W. Flake Oakley, IV
                                       ----------------------------------------
                                       W. Flake Oakley, IV
                                       Chief Financial Officer and
                                       Duly authorized agent for
                                       service