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


                                    FORM 11-K


                 Annual Report Pursuant to Section 15(d) of the
                         Securities Exchange Act of 1934



(Mark One)

[X]        Annual report pursuant to Section 15(d) of the Securities Exchange
           Act of 1934

                   For the fiscal year ended December 31, 2003


                                       Or


[  ]       Transition report pursuant to Section 15(d) of the Securities
           Exchange Act of 1934
           For the transition period from              to
                                          ------------    --------------

           Commission file number   1-8483


A. Full title of the plan and the address of the plan, if different from that of
the issuer named below:


                 MOLYCORP, INC. 401(K) RETIREMENT SAVINGS PLAN



B. Name of issuer of the securities held pursuant to the Plan and the address of
its principal executive office:

                               Unocal Corporation,
           2141 Rosecrans Avenue, Suite 4000, El Segundo, California 90245




                  MOLYCORP, INC. 401(k) RETIREMENT SAVINGS PLAN
                          INDEX TO FINANCIAL STATEMENTS



The following financial statements reflect the status of the Molycorp, Inc.
401(k) Retirement Savings Plan as of December 31, 2003 and 2002, and the results
of its transactions for each of the years then ended.


                                                                    Page Number



Report of Independent Auditors                                               1

Financial Statements:

     Statements of Net Assets Available for Benefits
        at December 31, 2003 and 2002                                        2

     Statements of Changes in Net Assets Available for Benefits
        for the years ended December 31, 2003 and 2002                       2

     Notes to Financial Statements                                          3-7

Signature                                                                    8

Supplemental Schedules*:

     Schedule of Assets (Held at Year End)                                   9

     Schedule of Reportable Transactions
        for the year ended December 31, 2003                                10

Exhibit Index                                                               11



* Supplemental schedules required by the Employee Retirement Income Security Act
of 1974  that are  omitted  are not  applicable  to the  Molycorp,  Inc.  401(k)
Retirement Savings Plan.


             REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM




To Participants and the Administrative Committee of the Molycorp, Inc.
401(k) Retirement Savings Plan:


         In our opinion, the accompanying statements of net assets available for
benefits and the related statements of changes in net assets available for
benefits present fairly, in all material respects, the net assets available for
benefits of Molycorp, Inc. 401(k) Retirement Savings Plan (the "Plan") at
December 31, 2003 and December 31, 2002, and the changes in net assets available
for benefits for the years then ended in conformity with accounting principles
generally accepted in the United States of America. These financial statements
are the responsibility of the Plan's management. Our responsibility is to
express an opinion on these financial statements based on our audits. We
conducted our audits of these statements in accordance with the standards of the
Public Company Accounting Oversight Board (United States). Those standards
require that we plan and perform the audit to obtain reasonable assurance about
whether the financial statements are free of material misstatement. An audit
includes examining, on a test basis, evidence supporting the amounts and
disclosures in the financial statements, assessing the accounting principles
used and significant estimates made by management, and evaluating the overall
financial statement presentation. We believe that our audits provide a
reasonable basis for our opinion.

         Our audits were conducted for the purpose of forming an opinion on the
basic financial statements taken as a whole. The supplemental schedules of
assets (held at end of year) , and reportable transactions for the year ended
December 31, 2003, are presented for the purpose of additional analysis and are
not a required part of the basic financial statements but are supplementary
information required by the Department of Labor's Rules and Regulations for
Reporting and Disclosure under the Employee Retirement Income Security Act of
1974. These supplemental schedules are the responsibility of the Plan's
management. The supplemental schedules have been subjected to the auditing
procedures applied in the audits of the basic financial statements and, in our
opinion, are fairly stated in all material respects in relation to the basic
financial statements taken as a whole.





PricewaterhouseCoopers LLP
Los Angeles, California
June 18, 2004






                  Molycorp, Inc. 401(k) Retirement Savings Plan
                 Statements of Net Assets Available for Benefits

                                                        December 31,
                                                  2003                2002
--------------------------------------------------------------------------------

                                                                
Investments at fair value                         $ 307,705           $ 173,721

                                             ---------------     ---------------
Net assets available for benefits                 $ 307,705           $ 173,721
                                             ===============     ===============



                  Molycorp, Inc. 401(k) Retirement Savings Plan
           Statements of Changes in Net Assets Available for Benefits

                                                   Year Ended December 31,
                                                   2003               2002
--------------------------------------------------------------------------------

Additions:
     Additions to (deductions from) net assets attributed to:
         Investment income (loss)
            Net appreciation (depreciation)
                                                                
               in fair value of investments         $ 28,962          $ (11,982)
            Interest                                     846              1,464
            Dividends                                  1,220                159
                                              ---------------     --------------
                 Total investment gain (loss)         31,028            (10,359)
                                              ---------------     --------------

     Contributions:
         Participant                                  94,552             40,375
         Company                                      16,834              2,233
                                              ---------------     --------------
                Total contributions                  111,386             42,608
                                              ---------------     --------------

             Total additions                         142,414             32,249
                                              ---------------     --------------

Deductions:
         Participant withdrawals
               and distributions                       8,430              1,198
                                              ---------------     --------------

             Total deductions                          8,430              1,198
                                              ---------------     --------------

           Net increase                              133,984             31,051
                                              ---------------     --------------

Net assets available for benefits:
           Beginning of year                         173,721            142,670
                                              ---------------     --------------
           End of year                             $ 307,705          $ 173,721
                                              ===============     ==============

                 See accompanying notes to financial statements.


                                      -2-




                          NOTES TO FINANCIAL STATEMENTS

NOTE 1 - DESCRIPTION OF THE PLAN

General
-------
         The Molycorp, Inc. 401(k) Retirement Savings Plan (the "Plan") is
sponsored by Molycorp, Inc. (the "Company"), an indirect wholly owned subsidiary
of Unocal Corporation. The Plan provides for voluntary pre-tax contributions by
participants, who are employees represented by collective bargaining agents at
certain facilities operated by the Company. The Plan's trustee and administrator
is Putnam Fiduciary Trust Company (the "Trustee"). Each participant is allowed
to choose how funds are invested from a range of investment fund options made
available through Putnam investments and Unocal Corporation common stock. The
Plan is subject to certain provisions of the Employee Retirement Income Security
Act of 1974 ("ERISA") as a defined contribution plan.

         The Plan booklets dated April 1, 1999, and December 1, 1996, constitute
part of a prospectus covering securities that has been registered under the
Securities Act of 1933. The April 1, 1999, and December 1, 1996, booklets can be
referenced for other information about the Plan.

Participation
-------------
         Regular, full-time employees are eligible to participate in the Plan
upon completion of six months of service.

Contributions
-------------
         Participant Contributions -- Participant contributions are voluntary
and are pre-tax. A participant's total annual pre-tax contribution limit was
raised to 75 percent from 50 percent of the participant's annual base pay. The
pre-tax contributions are also known as "401(k) contributions".

         Company Matching Contributions -- The Company matches employee pre-tax
401(k) contributions at the rate of 25 cents per dollar up to 6 percent of the
employee's total annual wage (base pay plus overtime pay).

         At its discretion, the Company directs the Trustee to purchase shares
attributable to Company matching contributions either on the open market or by
private purchases directly from the Company.

Participant Accounts
--------------------
         Each participant's account is credited with the participant's
contributions and increased or decreased by the respective investment earnings
or losses of the individual investments as governed by the participant's
investment selections.

Vesting
-------
         Participants are always 100 percent vested in participant contributions
and in the dividends and interest on those contributions. Vesting in the Company
contributions portion of participants' accounts and the dividends thereon is
based on years of vesting service. Participants are 100 percent vested in
Company contributions and dividends thereon after two years of vesting service.
Special vesting rules also apply to certain participants depending on the date
of and reason for termination of employment.

                                      -3-



Payment of Benefits
-------------------
         On termination of employment or at such time that participants become
eligible to receive benefits, participants may elect to receive their account
balances or defer their distributions until a later date, but no later than 60
days after the end of the plan year in which the latest of the following occurs:
April 1 after the close of the calendar year in which the participant attains
age 70 1/2, or two years after the participant's employment terminates. If a
participant continues to work after age 70 1/2, distribution of a portion of the
participant's account balance is required by April 1 of the calendar year
following the calendar year in which the participant attains age 70 1/2.

Federal Income Tax Status
-------------------------
         On May 30, 2002, the Company received a ruling, from the Internal
Revenue Service that the Plan meets the requirements of Section 401(a) of the
Internal Revenue Code (the "Code") of 1986, as amended, and that the Trust
established thereunder is entitled to exemption under the provisions of the
Code. The Plan has been amended since receiving the Internal Revenue Service
ruling. However, the plan administrator and the Plan's tax counsel believe the
Plan is currently designed and being operated in compliance with the applicable
requirements of the Code. Therefore, no provision for income taxes has been
included in the Plan's fiancial statements.

         The maximum employee pay eligible for benefit purposes under a
qualified plan was $200,000 per year for 2003. If an employee's pay exceeded
$200,000, only the first $200,000 of base pay was eligible for calculating
employee and Company contributions.

         Federal regulations place an annual dollar limit on the amount of
employee pre-tax contributions. The limit was $12,000 for 2003 and $11,000 for
2002. "Catch-up" contributions allow employees who were at least age 50 to
contribute an additional pre-tax contribution of $2,000 for 2003 and $1,000 for
2002. These limits are subject to adjustment in future years, in accordance with
federal regulations. If pre-tax contributions reach the annual limit before
year-end, they are suspended for the balance of the year. The Company matching
contributions are also suspended if the annual limit is reached before year-end.

         Withdrawals from the Plan are generally subject to federal income tax.
Also, withdrawals following termination of employment prior to age 55 may be
subject to an additional 10 percent federal penalty tax.

Plan Termination
----------------
         The Company expects to continue the Plan indefinitely, but, as future
conditions cannot be foreseen, the Company may at any time or from time to time
amend or terminate the Plan in whole or in part, subject to the requirements of
ERISA and other applicable laws. An amendment may affect present, as well as
future participants, but may not diminish the account of any participant
existing on the effective date of such amendment. The Company has no present
intent to terminate the Plan.

NOTE 2 - Summary of Significant Accounting Policies

Basis of Accounting

         The accompanying financial statements are prepared on the accrual basis
of accounting in conformity with accounting principles generally accepted in the
United States of America. In addition, the following accounting policies are
applied:

         a. Purchases and sales of securities are recorded on a trade-date
            basis.

         b. Dividends are recorded on an ex-dividend date basis.

         c. Interest income is recorded on the accrual basis.

         d. Benefits are recorded when paid.

                                      -4-


         The Plan presents in the statements of changes in net assets available
for benefits the net appreciation (depreciation) in the fair value of its
investments which consist of the realized gains or losses and the unrealized
appreciation (depreciation) on those investments.

Valuation of Investments
------------------------
         The Plan's investments are stated at fair value. Shares of registered
investment companies are valued at the net asset value of shares held by the
Plan at year-end. Shares of Unocal common stock are valued at the closing price
as reported for the New York Stock Exchange Composite Transactions at December
31, 2003 and 2002. Investments in common trust funds are valued based on
information provided by the Plan's investment custodian. The financial
statements of the common trust funds are audited annually by independent
auditors.

Use of Estimates in Preparation of the Financial Statements
-----------------------------------------------------------
         The preparation of financial statements in conformity with accounting
principles generally accepted in the United States of America requires the
Plan's management to make estimates and assumptions that affect the reported
amounts of assets and liabilities and disclosure of contingent assets and
liabilities at the dates of the financial statements and the reported amounts of
additions to and deductions from net assets during the reporting periods. Actual
results could differ from those estimates.

Risks and Uncertainties
-----------------------
The Plan invests in various investment securities. Investment securities are
exposed to various risks such as interest rate, market and credit risks. Due to
the level of risk associated with certain investment securities, it is at least
reasonably possible that changes in the values of investment securities will
occur in the near term and that such changes could materially affect
participants' account balances and the amounts reported in the statement of net
assets available for benefits.

                                      -5-



NOTE 3 - Investments

The following investments represent 5 percent or more of the Plan's net assets:


                                                         December 31,
                                                      2003          2002
------------------------------------------------------------------------------
                                                              
Putnam Money Market Fund
128,733 and 111,455 shares, respectively              $ 128,733     $ 111,455

Putnam New Opportunities Fund
1,108 and 794 shares, respectively                       42,992        23,170

Unocal Common Stock (a)
878 and 132 shares, respectively                         32,335         4,032

Putnam S&P 500 Index Fund
872 and 549 shares, respectively                         24,221        11,889

Vanguard Lifestrategy Moderate Growth Fund
1,194 and 0 shares, respectively                         19,828             -

Putnam International Growth Fund
763 and 655 shares, respectively                         15,857        10,829

(a)  Includes both participant and nonparticipant-directed amounts.


The Plan's investments appreciated or (depreciated) as follows:


                                                  December 31,
                                             2003             2002
---------------------------------------------------------------------
                                                       
Mutual funds                                $17,973          ($9,675)
Common or collective trust                    4,918           (2,202)
Common stock                                  6,071             (105)
                                        ------------    -------------
                                            $28,962         ($11,982)
                                        ============    =============

                                      -6-



Nonparticipant-Directed Investments
-----------------------------------
The nonparticipant-directed investments and the significant components of the
changes in those net assets are as follows:


                                                             December 31,
                                                        2003              2002
--------------------------------------------------------------------------------
Assets:
                                                                  
     Unocal common stock                             $ 23,395           $ 2,284
                                                    ----------        ----------
          Total assets                                 23,395             2,284

                                                    ----------        ----------
          Total nonparticipant-directed net assets   $ 23,395           $ 2,284
                                                    ==========        ==========



                                                       Year Ended December 31,
                                                        2003              2002
--------------------------------------------------------------------------------

Changes in net assets:
                                                                  
     Contributions                                   $ 16,834           $ 2,233
     Dividends                                            227                 -
     Net appreciation                                   4,418                51
     Benefits paid to participants                       (368)                -
                                                    ----------        ----------
          Net increase                               $ 21,111           $ 2,284
                                                    ==========        ==========


NOTE 4 - Parties-in-interest

         Certain of the Plan's investments are shares of mutual funds managed by
the Trustee, as defined by the Plan Agreement. Therefore, these transactions
qualify as party-in-interest transactions for which a statutory exemption
exists.

         Unocal Corporation, which also qualifies as a party-in-interest,
absorbs substantially all of the administrative expenses of the Plan, which were
nominal for the years ended December 31, 2003 and 2002. Such transactions with
the Company qualify for a statutory exemption.

                                      -7-


                                    SIGNATURE


Pursuant to the requirements of the Securities Exchange Act of 1934, the
Committee appointed by the Board of Directors of the Company to administer the
Plan has duly caused this annual report to be signed on its behalf by the
undersigned hereunto duly authorized.


                                 MOLYCORP, INC. 401(k) RETIREMENT SAVINGS PLAN


Date:  June 28, 2004                      By: /s/ William C. Schramm
                                              -------------------------------
                                              William C. Schramm
                                              Comptroller, Molycorp, Inc.

                                      -8-



                                   Molycorp, Inc. 401(k) Retirement Savings Plan
                                    Schedule of Assets (Held at End of Year) ***
                                               At December 31, 2003

     (a)                 (b)                                    (c)                                 (d)                 (e)
              Identity of Issuer,                    Description of Investment,
              Borrower, Lessor                    Including Maturity Date, Rate of
              or Similar Party              Interest, Collateral, Par, or Maturity Value            Cost           Current Value
------------------------------------------------------------------------------------------------------------------------------------
                                                                                                              
     **       Putnam Investments        Putnam Money Market Fund                                                          $ 128,733
                                        128,733 shares
     **       Putnam Investments        Putnam New Opportunities Mutual Fund                                                 42,992
                                        1,108 shares
      *       Unocal Corporation        Unocal Corporation Common Stock                              $26,321                 32,335
                                        878 shares
     **       Putnam Investments        Putnam S&P 500 Index Fund                                                            24,221
                                        872 shares
              Vanguard Group            Vanguard Life Strategy Moderate Growth Fund                                          19,828
                                        1,194 shares
     **       Putnam Investments        Putnam International Growth Fund                                                     15,857
                                        763 shares
     **       Putnam Investments        The Putnam Bond Index Fund                                                           10,999
                                        815 shares
     **       Putnam Investments        Putnam Voyager Fund                                                                  10,511
                                        644 shares
     **       Putnam Investments        George Putnam Fund of Boston                                                          8,442
                                        496 shares
              PIMCO Funds               PIMCO Renaissance Institutional Fund                                                  4,578
                                        196 shares
              Vanguard Group            The Vanguard Windsor II Fund                                                          2,639
                                        56 shares
              Vanguard Group            Vanguard Life Strategy Income Fund                                                    2,340
                                        177 shares
              Vanguard Group            Vanguard Life Strategy Conservative Growth Fund                                       2,187
                                        150 shares
              Vanguard Group            Vanguard Life Strategy Growth Fund                                                    2,043
                                        113 shares

                                                                                                                 -------------------
                                        Total assets held for investment purposes                                         $ 307,705
                                                                                                                 ===================

*   Parent of the Sponsor and employer and, therefore, a party-in-interest for which a statutory exemption exists.
**  Trustee for the Plan and, therefore, a party-in-interest for which a statutory exemption exists.
*** Under ERISA, an asset held for investment purposes is any asset held by the Plan on the last day of the Plan's
       fiscal year or acquired at any time during the Plan's fiscal year and disposed of at any time before the last day
       of the Plan's fiscal year, with certain exceptions.

                                      -9-



                                        Molycorp, Inc. 401(k) Retirement Savings Plan
                                           Schedule of Reportable Transactions (1)
                                                       December 31, 2003



 (a)                     (b)                    (c)           (d)       (e)     (f)          (g)            (h)               (i)
Identity of      Description of Assets                                         Expense                 Current Value of
  Party         (including Interest Rate     Purchase      Selling    Lease Incurred With   Cost        Asset on
 Involved    And Maturity in Case of a loan)   Price        Price     Rental Transaction  of Asset    Transaction Date    Net Gain
------------------------------------------------------------------------------------------------------------------------------------

                                                                                                   
Unocal
Corporation   (2)  Common Stock           $ 23,163                                     $ 23,163         $ 23,163
                     (30 transactions)

(1) Under ERISA, a reportable transaction is defined as a transaction or series of transactions during the Plan year that involves
    more than 5 percent of the fair value of the Plan's net assets at the beginning of the Plan year, with certain exceptions.

(2) Sponsor and employer and, therefore, a party-in-interest for which a statutory exemption exists.

                                      -10-



                                  EXHIBIT INDEX


 Exhibit 23      Consent of PricewaterhouseCoopers LLP




                                      -11-