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                                                                     EXHIBIT 5.1

                         [LATHAM & WATKINS LETTERHEAD]





                                 June 28, 2000









Leap Wireless International, Inc.
10307 Pacific Center Court
San Diego, CA 92121

               Re:    Leap Wireless International, Inc. Registration of 12 1/2%
                      Senior Notes due 2010 and 14 1/2% Senior Discount Notes
                      due 2010

Ladies and Gentlemen:

                In connection with the registration of up to $225,000,000
aggregate principal amount of 12 1/2% Senior Notes due 2010 (the "Senior Notes")
and up to $668,000,000 aggregate principal amount at maturity of 14 1/2% Senior
Discount Notes due 2010 (the "Senior Discount Notes," together with the Senior
Notes, the "Exchange Notes") by Leap Wireless International, Inc., a Delaware
corporation (the "Company"), under the Securities Act of 1933, as amended, on a
registration statement on Form S-4 filed with the Securities and Exchange
Commission (the "Commission") on May 17, 2000, as amended by Amendment No. 1 to
Form S-4, filed with the Commission on the date hereof (the "Registration
Statement"), you have requested our opinion with respect to the matters set
forth below. The Exchange Notes will be issued pursuant to an indenture dated as
of February 23, 2000 (the "Indenture") by and between the Company and State
Street Bank and Trust Company, as trustee (the "Trustee"). The Senior Notes and
Senior Discount Notes will be issued in exchange for the Company's outstanding
12 1/2% Senior Notes due 2010 and 14 1/2% Senior Discount Notes due 2010,
respectively, on the same terms set forth in the prospectus contained in the
Registration Statement and the Letter of Transmittal, filed as an exhibit
thereto. Capitalized terms used herein without definition have the meanings
assigned to them in the Indenture.

                In our capacity as your special counsel in connection with such
registration, we are familiar with the proceedings taken and proposed to be
taken by the Company in connection with the authorization and issuance of the
Exchange Notes, and for purposes of this opinion,
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June 28, 2000
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have assumed such proceedings will be timely completed in the manner presently
proposed and the terms of such issuance will otherwise be in compliance with
law. As such counsel, we have examined such matters of fact and questions of law
as we have considered appropriate for purposes of rendering the opinions
expressed below.

                In our examination, we have assumed the genuineness of all
signatures, the authenticity of all documents submitted to us as originals, and
the conformity to authentic original documents of all documents submitted to us
as copies.

                We have been furnished with, and with your consent have relied
upon, certificates of officers of the Company with respect to certain factual
matters. In addition, we have obtained and relied upon such certificates and
assurances from public officials as we have deemed necessary.

                We are opining herein as to the effect on the subject
transaction only of the federal laws of the United States, the internal laws of
the State of New York and the General Corporation Law of the State of Delaware,
and we express no opinion with respect to the applicability thereto, or the
effect thereon, of the laws of any other jurisdiction or, in the case of
Delaware, any other laws, or as to any matters of municipal law or the laws of
any local agencies within any state.

                Subject to the foregoing and the other matters set forth herein,
it is our opinion that, as of the date hereof, the Exchange Notes, when
authenticated by the Trustee and executed and delivered by the Company in
accordance with the terms of the Registration Rights Agreement and the
Indenture, will constitute legally valid and binding obligations of the Company,
enforceable against the Company in accordance with their terms, subject to the
following exceptions, limitations and qualifications:

(i)     the effect of bankruptcy, insolvency, fraudulent conveyances,
        reorganization, moratorium or other similar laws now or hereafter in
        effect relating to or affecting the rights or remedies of creditors,

(ii)    the effect of general principles of equity, whether enforcement is
        considered in a proceeding in equity or at law, and the discretion of
        the court before which any proceeding therefor may be brought;

(iii)   the unenforceability under certain circumstances under law or court
        decisions of provisions providing for the indemnification of or
        contribution to a party with respect to a liability where such
        indemnification or contribution is contrary to public policy;

(iv)    to the extent that enforceability may be limited due to the existence of
        an untrue statement of a material fact in the Registration Statement or
        omission to state a material fact therein necessary to make the
        statements in the Registration Statement not misleading; it being
        understood that we express no view with respect thereto;

(v)     the unenforceability of any provision requiring the payment of
        attorney's fees, except to the extent that a court determines such fees
        to be reasonable; and


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June 28, 2000
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(vi)    we express no opinion concerning the enforceability of the waiver of
        rights or defenses contained in Section 4.13 of the Indenture.

                To the extent that the obligations of the Company under the
Notes and the Indenture may be dependent upon such matters, we have assumed for
purposes of this opinion that the Trustee is duly organized, validly existing
and in good standing under the laws of its jurisdiction of organization; that
the Trustee is duly qualified to engage in the activities contemplated by the
Indenture; that the Indenture has been duly authorized, executed and delivered
by the Trustee and constitutes the legally valid and binding obligation of the
Trustee, enforceable against the Trustee in accordance with its terms; that the
Trustee is in compliance, generally and with respect to acting as a trustee
under the Indenture, with all applicable laws and regulations; and that the
Trustee has the requisite organizational and legal power and authority to
perform its obligations under the Indenture.

                We consent to your filing this opinion as an exhibit to the
Registration Statement and to the reference to our firm contained under the
heading "Legal Matters" in the prospectus included therein.


                                            Very truly yours,




                                            /s/ LATHAM & WATKINS