The Spielfeld–Trieste railway is a double-track, electrified main line in parts of Austria, Slovenia and Italy.

It runs from Spielfeld-Straß over the Austrian-Slovenian border at the Municipality of Šentilj, continuing via Maribor, Ljubljana and the Slovenian karst to the Adriatic port of Trieste, today in Italy.

The Southern Railway began construction work from Graz south to Celje (then called by its German name of Cilli) in 1843.

[A 1] The gap between Gloggnitz and Mürzzuschlag was closed in 1854 with the opening of the Semmering railway (Semmeringbahn), making the Vienna–Ljubljana line continuously trafficable.

The Southern Railway Company built its main workshop in Maribor (Marburg), which provided many jobs.

An efficient trade route was created for the entire empire, over which traffic could be carried out as far as the Middle East.

The railway was very beneficial to tourism: the Postojna Cave for example, which was on the line, was a well-known travel destination as early as the Biedermeier period.

The Austro-Hungarian Navy, which launched its new ships in Trieste and converted Pula into its main naval port, maintained contact with the Ministry of War in Vienna via the Southern Railway.

The so-called "Trieste railway question" or the campaign for a second rail connection with Trieste was established in 1891 and taken up by the Österreichischer Gewerbeverein (Austrian Trade Association) and the Österreichischer Ingenieur- und Architekten-Verein (Austrian Association of Engineers and Architects) and various considerations were discussed.

The European Union membership of all of these countries has made the movement of goods much easier, and participation in the Schengen Agreement has eliminated identity checks for passengers.