Exhibit 5.1

JONES DAY

555 SOUTH FLOWER STREET  ·  FIFTIETH FLOOR  ·  LOS ANGELES, CALIFORNIA  90071-2300

TELEPHONE: (213) 489-3939  ·  FACSIMILE: (213) 243-2539

September 9, 2011

Fluor Corporation

6700 Las Colinas Boulevard

Irving, Texas 75039

Re:                             $500,000,000 Aggregate Principal Amount of 3.375% Senior Notes due 2021

of Fluor Corporation

Ladies and Gentlemen:

We are acting as counsel for Fluor Corporation, a Delaware corporation (the “Company”), in connection with the issuance and sale of $500,000,000 aggregate principal amount of 3.375% Senior Notes due 2021 of the Company (the “Notes”), pursuant to the Underwriting Agreement, dated as of September 8, 2011 (the “Underwriting Agreement”), entered into by and among the Company and Merrill Lynch, Pierce, Fenner & Smith Incorporated and BNP Paribas Securities Corp., acting as representatives of the several underwriters named therein (collectively, the “Underwriters”).  The Notes will be issued pursuant to an indenture dated as of September 8, 2011 (the “Base Indenture”) between the Company and Wells Fargo Bank, National Association, as trustee (the “Trustee”), as amended and supplemented by a first supplemental indenture (the “First Supplemental Indenture” and, together with the Base Indenture, the “Indenture”), to be entered into between the Company and the Trustee.

In connection with the opinion expressed herein, we have examined such documents, records and matters of law as we have deemed relevant or necessary for purposes of such opinion.  Based on the foregoing, and subject to the further limitations, qualifications and assumptions set forth herein, we are of the opinion that the Notes, when they are executed by the Company and authenticated by the Trustee in accordance with the Indenture and issued and delivered to the Underwriters against payment therefor in accordance with the terms of the Underwriting Agreement, will constitute valid and binding obligations of the Company.

For purposes of the opinion expressed herein, we have assumed that (i) the definitive terms of the Notes will be established in accordance with the provisions of the Indenture and (ii) the Trustee has authorized, executed and delivered the Indenture and the Indenture is the valid, binding and enforceable obligation of the Trustee.

The opinion expressed herein is limited by bankruptcy, insolvency, reorganization, fraudulent transfer and fraudulent conveyance, voidable preference, moratorium or other similar laws and related regulations and judicial doctrines from time to time in effect relating to or affecting creditors’ rights generally, and by general equitable principles and public policy considerations, whether such principles and considerations are considered in a proceeding at law or at equity.

The opinion expressed herein is limited to the laws of the State of New York and the General Corporation Law of the State of Delaware, including the applicable provisions of the Delaware Constitution and the reported judicial decisions interpreting such law, in each case as currently in effect, and we express no opinion as to the effect of the laws of any other jurisdiction.

We hereby consent to the filing of this opinion as Exhibit 5.1 to the Current Report on Form 8-K dated the date hereof filed by the Company and incorporated by reference into the Registration Statement on Form S-3, as amended (Registration No. 333-156137) (the “Registration Statement”), filed by the Company to effect the registration of the Notes under the Securities Act of 1933 (the “Act”) and to the reference to Jones Day under the caption “Legal Matters” in the prospectus constituting a part of such Registration Statement.  In giving such consent, we do not thereby admit that we are included in the category of persons whose consent is required under Section 7 of the Act or the rules and regulations of the Securities and Exchange Commission promulgated thereunder.

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