The Austrian Southern Railway (German Südbahn) was a former railway company during the time of the Austro-Hungarian monarchy. Today, the term is still used to refer to the railway lines which were formerly operated by it.

Originally, the railway company operated services between Vienna and Trieste. The connection between Vienna and Gloggnitz was constructed from 1839 to 1842 by the private Wien-Gloggnitzer Eisenbahn, and the connection from Mürzzuschlag via Graz and Ljubljana to Trieste between 1842 and 1857 by the government. The two lines were connected by the Semmering Railway, when the railway over the Semmering was built according to plans made by Carl Ritter von Ghega between 1848 and 1854. In 1858, all lines were sold to the privately owned Südbahngesellschaft, which constructed another line from Maribor via Klagenfurt, Villach and Lienz to Franzensfeste . The company was nationalized only in 1923.

Today, the term Südbahn is commonly used within Austria for the railway from Vienna via Bruck an der Mur and Klagenfurt and Villach to Italy (Tarvisio), and the branch from Bruck to Graz and then to Slovenia.

The Vienna South Station was destroyed in World War II and rebuilt in 1956, when Vienna East Station was integrated into it. The railway from Vienna to Tarvisio had been equipped with electric power lines by 1963, the branch to Graz and Slovenia by 1966.