EXHIBIT 5.1

                                [Letterhead of]

                            CRAVATH, SWAINE & MOORE
                               [New York Office]









                                                              January 25, 2001


                                Teligent, Inc.
                      Registration Statement on Form S-3
                      ----------------------------------


Ladies and Gentlemen:

          We have acted as special counsel for Teligent, Inc., a Delaware
corporation (the "Company"), in connection with the filing by the Company with
the Securities and Exchange Commission (the "Commission") of a Registration
Statement on Form S-3 (the "Registration Statement") relating to sales by RGC
International Investors, LDC ("RGC") or its transferees of shares of Class A
Common Stock, $.01 par value per share, of the Company (the "Common Stock")
issued to RGC pursuant to the Common Stock Purchase Agreement, dated December
7, 2000, between the Company and RGC (the "Purchase Agreement") and the Stock
Purchase Warrant, dated December 7, 2000, of the Company in favor of RGC (the
"Warrant"). The Company is registering 136,551,317 shares of Common Stock
under the Registration Statement, which may be offered on a continuous or
delayed basis pursuant to the provisions of Rule 415 under the Securities Act
of 1933 (the "Securities Act").

          In connection with the foregoing, we have examined originals, or
copies certified or otherwise identified to our satisfaction, of such
documents, corporate records and other instruments as we have deemed necessary
for the purposes of this opinion, including without limitation the following:
(a) the Certificate of Incorporation, as amended, of the Company; (b) the
By-laws of the Company; (c) the Purchase Agreement and the Warrant; and (d)
the minutes of





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the special meeting of the Board of Directors of the Company held on
December 7, 2000.

          Based upon the foregoing, we are of opinion as follows:

          (1) The Company has been incorporated and is a validly existing
corporation under the laws of the State of Delaware.

          (2) When certificates representing the shares of Common Stock have
been duly executed, countersigned, registered and delivered either (i) in
accordance with the Purchase Agreement or (ii) upon exercise of the Warrant,
in accordance with its terms, then the shares of Common Stock will be
validly issued, fully paid and nonassessable.

          We are aware that we are referred to under the heading "Legal
Matters" in the prospectus forming a part of the Registration Statement, and
we hereby consent to such use of our name therein and to the use of this
opinion for filing with the Registration Statement as Exhibit 23.1 thereto.


                                            Very truly yours,


                                           /s/ Cravath, Swaine & Moore
                                           ------------------------------------
                                           Cravath, Swaine & Moore



Teligent, Inc.
     8065 Leesburg Pike, Suite 400
          Vienna, VA 22182