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                                                                     EXHIBIT 5.1

Mission Resources Corporation
1331 Lamar Street, Suite 1455
Houston, Texas  77010


            Re:   Distribution of up to 2,000,000 additional shares of Common
                  Stock of Mission Resources Corporation pursuant to the
                  Company's 1996 Stock Incentive Plan

Gentlemen:

We have acted as legal counsel for Mission Resources Corporation, a Delaware
corporation (the "Company"), in connection with the offer to certain eligible
employees of the Company and its subsidiaries of a total of up to 2,000,000
additional shares (the "Shares") of the Company's common stock, $.01 par value
per share (the "Common Stock"), issuable pursuant to the Company's 1996 Stock
Incentive Plan (the "Plan").

We have made such inquiries and examined such documents as we have considered
necessary or appropriate for the purposes of giving the opinion hereinafter set
forth, including the examination of executed or conformed counterparts, or
copies certified or otherwise proved to our satisfaction of the following:

         (i)   the Certificate of Incorporation of the Company as filed with the
               Secretary of State of Delaware on March 7, 1994, as amended;

         (ii)  the Bylaws of the Company as of the date of this opinion;

         (iii) the Company's Registration Statement on Form S-8 covering the
               Shares (the "Registration Statement");

         (iv)  the Plan, as amended; and

         (v)   such other documents, corporate records, certificates and other
               instruments as we have deemed necessary or appropriate for the
               purpose of this opinion.

In making the foregoing examination, we have assumed the genuineness of all
signatures and the authenticity of all documents submitted to us as originals,
and the conformity to original documents of all documents submitted to us as
certified or photostatic copies and the due authorization, execution, delivery
or recordation of all documents where due authorization, execution or
recordation are prerequisites to the effectiveness thereof. Furthermore, we have
assumed that prices paid for shares of Common Stock will equal or exceed the par
value per share of the Common Stock. As to questions of fact material to this
opinion, where such facts have not been independently established, and as to the
content and form of the Certificate of Incorporation (as amended), Bylaws (as
amended), Plan (as amended), minutes, records, resolutions and other documents
or writings of the Company, we have relied, to the extent we deem reasonably
appropriate, upon representations or certificates of officers of the Company and
upon documents, records and instruments furnished to us by the Company, without
independent check or verification of their accuracy.

Based upon the foregoing, and having regard for such legal considerations as we
deem relevant, we are of the opinion that the Shares of Common Stock covered by
the Registration Statement, which may be issued from time to time in accordance
with the terms of the Plan, have been duly authorized for issuance by the
Company, and, when so issued in accordance with the terms and conditions of the
Plan, will be validly issued, fully paid and nonassessable.

We hereby consent to the filing of this opinion with the SEC as an exhibit to
the Registration Statement.


                                       Very truly yours,


                                       /s/ Haynes and Boone, L.L.P.
                                       --------------------------------
                                       HAYNES AND BOONE, L.L.P.
Houston, Texas
June 20, 2001