<PAGE>
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                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                            ------------------------

                                  FORM 10-K/A

<TABLE>
<C>        <S>
(MARK ONE)

   /X/     ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE
           SECURITIES EXCHANGE ACT OF 1934

              FOR THE FISCAL YEAR ENDED DECEMBER 31, 1999

                                  OR

   / /     TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE
           SECURITIES EXCHANGE ACT OF 1934

                     COMMISSION FILE NO. 000-23087
</TABLE>

                   STARTEC GLOBAL COMMUNICATIONS CORPORATION
             (Exact name of registrant as specified in its charter)

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<S>                                                 <C>
                     DELAWARE                                           52-2099559
         (State or Other Jurisdiction of                             (I.R.S. Employer
          Incorporation or Organization)                           Identification No.)
</TABLE>

                             10411 MOTOR CITY DRIVE
                               BETHESDA, MD 20817
                    (Address of principal executive offices)

                                 (301) 365-8959

              (Registrant's telephone number, including area code)

          Securities registered pursuant to Section 12(b) of the Act:
                                      None

          Securities registered pursuant to Section 12(g) of the Act:

                    COMMON STOCK, PAR VALUE $0.01 PER SHARE
                                (Title of class)

    Indicate by check mark whether the registrant (1) has filed all reports
required to be filed by Section 13 or 15(d) of the Securities Exchange Act of
1934 during the preceding 12 months (or for such shorter period that the
registrant was required to file such reports), and (2) has been subject to such
filing requirements for the past 90 days. Yes /X/ No / /

    Indicate by check mark if disclosure of delinquent filers pursuant to Item
405 of Regulation S-K is not contained herein, and will not be contained, to the
best of the registrants' knowledge, in definitive proxy or information
statements incorporated by reference in Part III of this Form 10-K or any
amendment to this Form 10-K. / /

    Non-affiliates of the Registrant held approximately 8,123,119 shares of
Common Stock as of March 22, 2000. The fair market value of the stock held by
non-affiliates is approximately $218,816,518 based on the sale price of the
shares on March 22, 2000.

    As of March 22, 2000, 12,109,410 shares of Common Stock, par value $0.01,
were outstanding.

                   DOCUMENTS INCORPORATED BY REFERENCE: None.

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<PAGE>
                                    PART IV

ITEM 14. EXHIBITS, FINANCIAL STATEMENT SCHEDULES, AND REPORTS ON FORM 8-K

    The following documents are filed as part of this Annual Report on
Form 10-K:

    (a) 1. FINANCIAL STATEMENTS. The financial statements of the Company and the
           related Report of Independent Public Accountants are filed as Item 8
           hereof.

    (a) 2. FINANCIAL STATEMENT SCHEDULE. The Financial Statement Schedule
           described below is filed as part of this report.

          Description:

          Report of Independent Public Accountants Schedule II--Valuation and
          Qualifying Accounts

    (a) 3. EXHIBITS. The Exhibits required to be filed pursuant to Form 10-K are
           identified in the Exhibit Index.

    (b) REPORTS ON FORM 8-K

    During the last quarter of 1999, we filed two reports on Form 8-K with the
SEC on November 9 and December 30 to file certain press releases under Item 5 of
Form 8-K.

<PAGE>
                                   SIGNATURES

    Pursuant to the requirements of Section 13 or 15(d) of the Securities
Exchange Act of 1934, as amended, the Registrant has duly caused this Report to
be signed on its behalf by the undersigned, thereunto duly authorized this 27th
day of March 2000.

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<S>                                                    <C>  <C>
                                                       STARTEC GLOBAL COMMUNICATIONS CORPORATION

                                                       By   /s/ PRABHAV V. MANIYAR
                                                            -----------------------------------------
                                                            Prabhav V. Maniyar
                                                            Chief Financial Officer
</TABLE>

    Pursuant to the requirements of the Securities Exchange Act of 1934, this
report has been signed below by the following persons on behalf of the
Registrant and in the capacities and on the dates indicated.

                   STARTEC GLOBAL COMMUNICATIONS CORPORATION

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<CAPTION>
              SIGNATURE                                TITLE                       DATE
              ---------                                -----                       ----
<S>                                    <C>                                    <C>
/s/ RAM MUKUNDA                        President, Chief Executive Officer,    March 27, 2000
------------------------------------   Treasurer and Chairman (Principal
Ram Mukunda                            Executive Officer)

/s/ PRABHAV V. MANIYAR                 Chief Financial Officer and Director   March 27, 2000
------------------------------------   (Principal Financial and Accounting
Prabhav V. Maniyar                     Officer)

/s/ SUDHAKAR V. SHENOY                 Director                               March 27, 2000
------------------------------------
Sudhakar V. Shenoy

/s/ NAZIR G. DOSSANI                   Director                               March 27, 2000
------------------------------------
Nazir G. Dossani

/s/ RICHARD K. PRINS                   Director                               March 27, 2000
------------------------------------
Richard K. Prins
</TABLE>

<PAGE>
                                 EXHIBIT INDEX

<TABLE>
<CAPTION>
       EXHIBIT
       NUMBER                                   DESCRIPTION
---------------------   ------------------------------------------------------------
<S>                     <C>
 2.1****                Agreement and Plan of Reorganization dated June 30, 1998 by
                        and between Startec Global Communications Corporation and
                        Startec Global Holding Corporation

 3.1****                Restated Certificate of Incorporation.

 3.2****                Bylaws.

 4.1*                   Specimen of Common Stock Certificate.

 4.2*                   Warrant Agreement dated as of July 1, 1997 by and between
                        Startec, Inc. and Signet Bank.

 4.3*                   Form of Underwriters' Warrant Agreement (including Form of
                        Warrant).

 4.4*                   Voting Agreement dated as of July 31, 1997 by and between
                        Ram Mukunda and Vijay and Usha Srinivas.

 4.5***                 Indenture, dated as of May 21, 1998, between the Company and
                        First Union National Bank.

 4.6***                 Form of 12% Series A Senior Notes due 2008

 4.7***                 Registration Rights Agreement, dated as of May 21, 1998,
                        among the Company, Lehman Brothers Inc., Goldman Sachs & Co.
                        and ING Barings (U.S.) Securities, Inc.

 4.8***                 Warrant Agreement, dated as of May 21, 1998 by and between
                        the Company and First Union National Bank, a Warrant Agent

 4.9***                 Form of Warrant (included as Exhibit A to Exhibit 4.8)

 4.10***                Collateral Pledge and Security Agreement, dated as of May
                        21, 1998 by and between the Company and First Union National
                        Bank, as Trustee

 4.11**                 Rights Agreement, dated as of March 26, 1998, between the
                        Company and Continental Stock Transfer & Trust Company.

4.12++++                First Supplemental Indenture dated as of 20 August 1999 by
                        and between the Company and First Union National Bank, as
                        Trustee

10.1*                   Secured Revolving Line of Credit Facility Agreement dated as
                        of July 1, 1997 by and between Startec, Inc. and Signet
                        Bank.

10.2*                   Lease by and between Vaswani Place Limited Partnership and
                        Startec, Inc. dated as of September 1, 1994, as amended.

10.3*                   Agreement by and between World Communications, Inc. and
                        Startec, Inc. dated as of April 25, 1990.

10.4*                   Co-Location and Facilities Management Services Agreement by
                        and between Extranet Telecommunications, Inc. and Startec,
                        Inc. dated as of August 28, 1997.

10.5*                   Employment Agreement dated as of July 1, 1997 by and between
                        Startec, Inc. and Ram Mukunda.

10.6*                   Employment Agreement dated as of July 1, 1997 by and between
                        Startec, Inc. and Prabhav V. Maniyar.

10.7*                   Amended and Restated Stock Option Plan.

10.8*                   1997 Performance Incentive Plan.

10.9*                   Subscription Agreement by and among Blue Carol Enterprises,
                        Limited, Startec, Inc. and Ram Mukunda dated as of February
                        8, 1995.
</TABLE>

<PAGE>

<TABLE>
<CAPTION>
       EXHIBIT
       NUMBER                                   DESCRIPTION
---------------------   ------------------------------------------------------------
<S>                     <C>
10.10*                  Agreement for Management Participation by and among Blue
                        Carol Enterprises, Limited, Startec, Inc. and Ram Makunda
                        dated as of February 8, 1995, as amended as of June 16,
                        1997.

10.11*                  Service Agreement by and between Companhia Santomensed De
                        Telecommunicacoes and Startec, Inc. as amended on February
                        8, 1995.

10.12*+                 Lease Agreement between Companhia Protuguesa Radio Marconi,
                        S.A. and Startec, Inc. dated as of June 15, 1996.

10.13*+                 Indefeasible Right of Use Agreement between Companhia
                        Portuguesa Radio Marconi, S.A. and Startec, Inc. dated as of
                        January 1, 1996.

10.14*+                 International Telecommunication Services Agreement between
                        Videsh Sanchar Nigam Ltd. and Startec, Inc. dated as of
                        November 12, 1992.

10.15*+                 Digital Service Agreement with Communications Transmission
                        Group, Inc. dated as of October 25, 1994.

10.16*+                 Lease Agreement by and between GPT Finance Corporation and
                        Startec, Inc. dated as of January 10, 1990.

10.17*+                 Carrier Services Agreement by and between Frontier
                        Communications Services, Inc. and Startec, Inc. dated as of
                        February 26, 1997.

10.18*+                 Carrier Services Agreement by and between MFS International,
                        Inc. and Startec, Inc. dated as of July 3, 1996.

10.19*+                 International Carrier Voice Service Agreement by and between
                        MFS International, Inc. and Startec, Inc. dated as of June
                        6, 1996.

10.20*+                 Carrier Services Agreement by and between Cherry
                        Communications, Inc. and Startec, Inc. dated as of June 7,
                        1995.

10.21***                Agreement by and between Northern Telecom Inc. and the
                        Company, dated as of December 23, 1997

10.22***                Indefeasible Right of Use Agreement by and between
                        Telegloble Cantat-3, Inc. and the Company, dated as of
                        September 15, 1997 (Canus 1 Cable System).

10.23***                Indefeasible Right of Use Agreement by and between Teleglobe
                        Cantat-3, Inc. and the Company, dated as of September 15,
                        1997 (Cantat 3 Cable System).

10.24#                  Loan and Security Agreement by and between Prabhav V.
                        Maniyar and the Company, dated June 30, 1998 (as amended and
                        related by agreement dated December 31, 1998. See Exhibit
                        10.41 below).

10.25#                  Lease by and between The Vaswani Place Corporation and the
                        Company, dated as of October 27, 1998.

10.26#                  Indefeasible Right of Use Agreement by and between Cable &
                        Wireless Inc. and the Company, dated June 9, 1998 (Gemini
                        Cable System)

10.27#                  First Amendment to Lease by and between The Vaswani Place
                        Corporation and the Company, dated May 11, 1998.

10.28#                  International Facilities License, United Kingdom

10.29##                 Columbus III Cable System Construction and Maintenance
                        Agreement dated February 11, 1998.

10.30###                TAT-14 Cable Network Construction and Maintenance Agreement
                        dated as of September 2, 1998.

10.31###                SEA-ME-WE Construction and Maintenance Agreement dated as of
                        January 1, 1997.
</TABLE>

<PAGE>

<TABLE>
<CAPTION>
       EXHIBIT
       NUMBER                                   DESCRIPTION
---------------------   ------------------------------------------------------------
<S>                     <C>
10.32###                Amendment dated as of July 8, 1998 by and between Cable &
                        Wireless, Inc. and the Company to the Indefeasible Right of
                        Use Agreement, dated as of June 9, 1998 (Gemini Cable
                        System).

10.33###                Rack Space Agreement by and between Americatel Corporation
                        and the Company, dated as of July 27, 1998.

10.34###                Rack Space Agreement by and between IXC Carrier, Inc. and
                        the Company, dated as of July 6, 1998 (Los Angeles).

10.35###                Rack Space Agreement by and between IXC Carrier, Inc. and
                        the Company, dated as of August 19, 1998 (Dallas).

10.36###                Co-Location Agreement by and between Espirit Telecom Benelux
                        BV and the Company., dated as of September 21, 1998

10.37###                Sublease Agreement by and between Information Systems &
                        Networks, Inc. and the Company dated as of August 11, 1998.

10.38###                Master Supply Agreement by and between TTN, Inc. and the
                        Company dated as of September 21, 1998.

10.39#####              Loan and Security Agreement by and between NTFC Capital
                        Corporation and the Company, dated as of December 31, 1998.

10.40#####              Loan and Security Agreement by and between Ram Mukunda and
                        the Company, dated as of October 8, 1998.

10.41#####              Loan and Security Agreement by and between Prabhav V.
                        Maniyar and the Company, dated as of December 31, 1998.

10.42#####              TPC-5 Cable Network IRU Agreement between Companhia
                        Portuguesa Radio Marconi, SA and the Company, dated December
                        15, 1998.

10.43#####              TPC-5 Cable Network Indefeasible Right of Use Agreement
                        between KDD Corporation and the Company dated December 31,
                        1998.

10.44#####              TAT-12/13 Cable Network IRU Agreement between Companhia
                        Portuguesa Radio Marconi, SA and the Company, dated December
                        15, 1998.

10.45#####              Lease between 36 North East Second Street, L.L.C and the
                        Company executed on November 30, 1998.

10.46#####              Lease between 36 North East Second Street, L.L.C and the
                        Company executed on October 29, 1998.

10.47####               Stock Purchase Agreement dated as of November 30, 1998 by
                        and between the Company and Pacific Systems Corporation

10.48####               Quota Purchase Agreement by and between Martin Otten and
                        Rolf Otten, on the one part, and the Company, on the other
                        part, effective as of December 31, 1998.

10.49++                 Sublease Agreement by and between Ceridian Corporation and
                        the Company dated January 8, 1999.

10.50+++                Purchase and License Agreement between Ascend Communications
                        Inc. and Startec Global Operating Company dated on May 5,
                        1999.

10.51+++                Term Lease Master Agreement between IBM Corporation and
                        Startec Global Operating Company dated as of June 22, 1999.

10.52+++                Loan and Security Agreement between Congress Financial
                        Corporation and Startec Global Operating Company dated as of
                        June 29, 1999.
</TABLE>

<PAGE>

<TABLE>
<CAPTION>
       EXHIBIT
       NUMBER                                   DESCRIPTION
---------------------   ------------------------------------------------------------
<S>                     <C>
10.53+++                Lease Agreement between the Rector, Church Wardens and
                        Vestryment of Trinity Church in the City of New York and the
                        Company dated as of April 23, 1999.

10.54++++               Billing and Collection Services Agreement between BC Tel
                        Corporation and Startec Global Communications Company
                        (Canada) dated 23 July, 1999.

10.55++++               Procedures of the Interexchange Carrier Group Agreement
                        between BC Tel Corporation and Startec Global Communications
                        Company (Canada) dated July 23, 1999.

21.1                    Subsidiaries of Company.

23.1                    Consent of Arthur Andersen LLP.

27.1                    Financial Data Schedule.
</TABLE>

------------------------

<TABLE>
<S>   <C>
*     Incorporated by reference from the Company's Registration
      Statement on Form S-1 (SEC File No. 333-32753).
**    Incorporated by reference from the Company's Current Report
      on Form 8-K filed on April 8, 1998
***   Incorporated by reference from the Company's Quarterly
      Report on Form 10-Q for the quarter ended June 30, 1998
****  Incorporated by reference from the Company's Registration
      Statement on Form S-4 (SEC File No. 333-58247)
#     Incorporated by reference from the Company's Registration
      Statement on Form S-4 (SEC File No. 333-61779)
##    Incorporated by reference from the Company's Registration
      Statement on Form S-1 (SEC File No. 333-64465)
###   Incorporated by reference from the Company's Quarterly
      Report on Form 10-Q for the quarter ended September 30,
      1998.
####  Incorporated by reference from the Company's Current Report
      on Form 8-K/A filed on February 12, 1999.
##### Incorporated by reference from the Company's Annual report
      on Form 10-K for the fiscal year ended 1998.
+     Portions of the Exhibit have been omitted pursuant to a
      grant of Confidential Treatment by the Securities and
      Exchange Commission under Rule 406 of the Securities Act of
      1933, as amended, and the Freedom of Information Act.
++    Incorporated by reference from the Company's Quarterly
      Report on Form 10-Q for the quarter ended March 31, 1999.
+++   Incorporated by reference from the Company's Quarterly
      Report on Form 10-Q for the quarter ended June 30, 1999.
++++  Incorporated by reference from the Company's Quarterly
      Report on Form 10-Q for the quarter ended September 30,
      1999.
</TABLE>