The Vienna Stadtbahn was a rail-based public transportation system operated under this name from 1898 until 1989. Today, the Vienna U-Bahn lines U4 and U6 and the Vienna S-Bahn run on its former lines.

The Vienna U-Bahn, where U-Bahn is an abbreviation of the German word Untergrundbahn, is a rapid transit system serving Vienna, Austria. The five-line network consists of 83.1 kilometers (51.6 mi) of route, serving 109 stations. 459.8 million passengers rode the U-Bahn in 2019. The network is undergoing expansion and rolling stock renewal. Since 1969, 200 million euros have been invested annually in the extension of the Vienna U-Bahn.