1

                                                                       EXHIBIT 5

                          GIBSON, DUNN & CRUTCHER LLP
                                Jamboree Center
                                  4 Park Plaza
                         Irvine, California 92614-8557
(949) 451-3800                                                     C 29019-00873


                                January 22, 1999


Fluor Corporation
3353 Michelson Drive
Irvine, CA  92698

         Re:      Fluor Corporation Registration Statement on Form S-3

Ladies and Gentlemen:

         At your request, we have examined the Registration Statement on Form
S-3 (together with the exhibits thereto, the "Registration Statement"), and the
prospectus (the "Prospectus") forming a part thereof, in connection with the
registration and sale of up to $500,000,000 in aggregate initial offering price
of the debt securities, issuable in various series (the "Debt Securities"), of
Fluor Corporation, a Delaware corporation (the "Company"). The Prospectus
provides that it will be supplemented in the future by one or more supplements
to the Prospectus (each, a "Prospectus Supplement").

         In addition, we have examined the originals, or copies identified to
our satisfaction as being true and complete copies of the originals, of the
following documents: (i) the Company's Restated Certificate of Incorporation and
Bylaws, each as amended to the date hereof; (ii) the Indenture, dated as of
February 18, 1997 (the "Indenture"), by and between the Company and Bankers
Trust Company, as trustee (the "Trustee"); and (iii) such other documents and
records of corporate proceedings and other actions taken by the Company in
connection with the authorization, issuance and sale of the Debt Securities.

         In our examination, we have assumed the genuineness of all signatures
on, and the authenticity of, all documents submitted to us as originals and the
conformity to the original documents of all documents submitted to us as copies.
With respect to agreements and instruments executed by natural persons, we have
assumed the legal competency and authority of such persons. As to facts material
to the opinion expressed herein which were not independently 

   2

Fluor Corporation
January 22, 1999
Page 2



established or verified by us, we have relied upon oral or written statements
and representations of the Company and others.

         We have assumed with your permission that: (a) the Trustee had, has and
will have all requisite power and authority to execute, deliver and perform its
obligations under the Indenture and any applicable officer's certificate or
supplemental indenture as provided by the terms of the Indenture (each, a
"Supplemental Indenture"), (b) the execution and delivery of the Indenture and
any applicable Supplemental Indenture and the performance of the Trustee's
obligations thereunder have been and will be duly authorized by all necessary
action on the Trustee's part and the Indenture and any applicable Supplemental
Indenture have been and will be duly delivered by the Trustee, and (c) the
Indenture and any applicable Supplemental Indenture are and will be enforceable
against the Trustee in accordance with their terms.

         Based upon the foregoing and in reliance thereon, and subject to the
qualifications, exceptions, assumptions and limitations herein contained, we are
of the opinion that, when (1) the Debt Securities have been duly established in
accordance with the terms of the Indenture and any applicable Supplemental
Indenture, (2) the Debt Securities have been duly executed and delivered and
have been duly authenticated by the Trustee and have been duly executed and
delivered on behalf of the Company against payment therefor, all in accordance
with the terms and provisions of the Indenture and any applicable Supplemental
Indenture and as contemplated by the Registration Statement, the Prospectus and
any related Prospectus Supplement, and (3) each of the Registration Statement
and any required post-effective amendments thereto have become effective under
the Securities Act of 1933, as amended (the "Securities Act"), the Debt
Securities will constitute valid and legally binding obligations of the Company,
enforceable in accordance with their terms.

         The opinion set forth above is subject to the following exceptions,
limitations and qualifications: (A) the effect of applicable bankruptcy,
insolvency, reorganization, moratorium and other similar laws and court
decisions of general application, including without limitation, statutory or
other laws regarding fraudulent or preferential transfers relating to, limiting
or affecting the enforcement of creditors' rights generally and laws affecting
distribution by corporations to stockholders; (B) the application of general
principles of equity, including without limitation, concepts of materiality,
reasonableness, good faith and fair dealing, regardless of whether such
enforceability is considered in a proceeding at law or in equity; and (C) we
express no opinion with respect to the enforceability of any provision in the
Indenture or any applicable Supplemental Indenture regarding rights of indemnity
or contribution where such provision is limited by applicable federal or state
law or contrary to public policy.

         We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement, and we further consent to the use of our name under the
caption "Legal Matters" in the Registration Statement, the Prospectus and any
related Prospectus Supplement. In giving this 
   3

Fluor Corporation
January 22, 1999
Page 3


consent, we do not thereby admit that we are within the category of persons
whose consent is required under Section 7 of the Securities Act or the Rules and
Regulations of the Securities and Exchange Commission.

                                              Very truly yours,

                                              /s/ GIBSON, DUNN & CRUTCHER LLP
                                              -------------------------------
                                              GIBSON, DUNN & CRUTCHER LLP

TDM/JMW/GCT