EXHIBIT 5

[CONSENT OF COMPANY COUNSEL]


                                               Unocal Corporation
                                               2141 Rosecrans Avenue, Suite 4000
                                               El Segundo, California  90245
                                               Telephone (310) 726-7651
                                               Facsimile (310) 726-7815



                                  UNOCAL [LOGO]


Dennis P.R. Codon
Senior Vice President, Chief Legal Officer and General Counsel



                                November 15, 2001


        Re:    Registration on Form S-8 of  Unocal Corporation (the "Company")

Ladies and Gentlemen:

        At your request, and as General Counsel of the Company, I have examined
the Registration Statement on Form S-8 to be filed with the Securities and
Exchange Commission in connection with the registration under the Securities Act
of 1933, as amended, of $40,000,000 [Forty Million Dollars] of Deferred
Compensation Obligations of the Company (the "Obligations"), to be issued
pursuant to the Unocal Deferred Compensation Plan (the "Plan"). I have examined
the Plan and am familiar with the proceedings taken by the Company in connection
with the authorization of the Plan, and the authorization, registration, and
offering of the Obligations.

        Based upon such examination and upon such matters of fact and law as I
have deemed relevant, I am of the opinion that:

               (1)    the Obligations have been duly authorized by all necessary
                      corporate action on the part of the Company;

               (2)    when incurred in accordance with such authorization, the
                      provisions of the Plan and relevant elections and
                      agreements duly authorized by and in accordance with the
                      terms of the Plan, the Obligations will be legally valid
                      and binding obligations of the Company, enforceable
                      against the Company in accordance with their terms, except
                      as may be limited by bankruptcy, insolvency,
                      reorganization, moratorium or similar laws relating to or
                      affecting creditors' rights generally (including, without
                      limitation, fraudulent conveyance laws), and by general
                      principles of equity including, without limitation,
                      concepts of materiality, reasonableness, good faith and
                      fair dealing and the possible unavailability of specific





                      performance or injunctive relief, regardless of whether
                      considered in a proceeding in equity or at law; and

               (3)    the participants will not, solely by virtue of their
                      status as participants, be held liable for assessments by
                      the Company against amounts previously deferred, except
                      for required withholding and other payroll or similar
                      deductions, and other charges or adjustments, referenced
                      in or contemplated by the Registration Statement and the
                      terms of the Plan.

        I consent to the use of this opinion as an exhibit to the Registration
Statement.

                                            Respectfully submitted,


                                            /s/ DENNIS P.R. CODON


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