EXHIBIT 5.1


                             Vinson & Elkins L.L.P.
                         1001 Fannin Street, Suite 2300
                             Houston, Texas  77002



                                  May 10, 2001


ATP Oil & Gas Corporation
4600 Post Oak Place, Suite 200
Houston, Texas  77027


Ladies and Gentlemen:


  We have acted as counsel for ATP Oil & Gas Corporation, a Texas corporation
(the "Company"), with respect to certain legal matters in connection with the
registration by the Company under the Securities Act of 1933, as amended (the
"Securities Act"), of the offer and sale of up to 4,646,607 shares (the
"Shares") of common stock, par value $.001 per share, of the Company issuable
upon exercise of options under the ATP Oil and Gas Corporation 1998 Stock
Option Plan and the ATP Oil and Gas Corporation 2000 Stock Plan (the "Plans").

  In connection with the foregoing, we have examined or are familiar with the
Amended and Restated Articles of Incorporation of the Company, the Restated
Bylaws of the Company, the Plans and the Registration Statement on Form S-8
filed in connection with the registration of the Shares (the "Registration
Statement"), and such other certificates, instruments and documents as we have
considered necessary or appropriate for purposes of this opinion.

  Based upon the foregoing, we are of the opinion that the Shares have been duly
authorized and, when the Shares are issued in accordance with the provisions of
the Plans, will be validly issued and fully paid and non-assessable.

  The foregoing opinion is limited to the laws of the United States of America
and the State of Texas.  For purposes of this opinion, we assume that the Shares
will be issued in compliance with all applicable state securities or Blue Sky
laws.

  We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement. In giving this consent, we do not admit that we are
within the category of persons whose consent is required under Section 7 of the
Securities Act and the rules and regulations thereunder.

                                          Very truly yours,

                                          /s/ VINSON & ELKINS L.L.P.

                                          VINSON & ELKINS L.L.P.