The Southern Railway is a railway in Austria that runs from Vienna to Graz and the border with Slovenia at Spielfeld via Semmering and Bruck an der Mur. Along with the Spielfeld-Straß–Trieste railway, it forms part of the Austrian Southern Railway that connected Vienna with Trieste, the main seaport of the Austro-Hungarian Monarchy, via Ljubljana. A main obstacle in its construction was getting over the Semmering Pass over the Northern Limestone Alps. The twin-track, electrified section that runs through the current territory of Austria is owned and operated by Austrian Federal Railways (ÖBB) and is one of the major lines in the country.

The Semmering railway in Austria, which starts at Gloggnitz and leads over the Semmering to Mürzzuschlag, was the first mountain railway in Europe built with a standard gauge track. It is commonly referred to as the world's first true mountain railway, given the very difficult terrain and the considerable altitude difference that was mastered during its construction. It is still fully functional as a part of the Southern Railway which is operated by the Austrian Federal Railways.