EXHIBIT 23 CONSENT OF INDEPENDENT ACCOUNTANTS We hereby consent to the incorporation by reference in the Registration Statement on Form S-8 (No. 33-43309) of Unocal Corporation of our report, dated May 24, 2002, relating to the financial statements of the Molycorp, Inc. 401(k) Retirement Savings Plan, which appears in this Form 11-K. /s/PricewaterhouseCoopers LLP PricewaterhouseCoopers LLP Los Angeles, California June 28, 2002