Exhibit 23.1 Consent of Ernst & Young LLP CONSENT OF ERNST & YOUNG LLP, INDEPENDENT AUDITORS We consent to the incorporation by reference in the Registration Statement (Form S-8), pertaining to the Amended and Restated 1992 Stock Option Plan of Global TeleSystems Group, Inc., of our reports dated December 16, 1997 (Global TeleSystems Group, Inc.), February 21, 1997 (EDN Sovintel), and December 23, 1997 (Hermes Europe Railtel B.V.), included in the Registration Statement on Form S-1 (No. 333-36555) of Global TeleSystems Group, Inc., filed with the Securities and Exchange Commission. /s/Ernst & Young LLP Vienna, Virginia February 4, 1998