The Arlberg Railway Tunnel with a length of 10.6 kilometres (6.6 mi) is the central part of the Arlberg railway in western Austria between the provinces of Tyrol and Vorarlberg. The tunnel runs through the Arlberg massif at the northeastern end of the Rhaetian Alps.
It opened on December 21, 1884 as a single-track tunnel. The traffic through the tunnel grew so quickly, that a second track was opened by July 15, 1885. It starts kilometre 99.5 in the station of St. Anton am Arlberg and ends in Langen am Arlberg.