The Südostbahn (Swiss South Eastern Railway) – commonly abbreviated to SOB – is a railway company and 1,435 mm (4 ft 8 1⁄2 in) standard gauge network in Switzerland.
The Südostbahn is a small private railway, i.e. jointly owned by the cantonal and federal governments as an Aktiengesellschaft (AG). At the end of 2001, the previous SOB merged with the Bodensee–Toggenburg railway (BT) to form the Südostbahn (SOB).
The Schweizerische Südostbahn AG operates from Romanshorn on Lake Constance via St. Gallen, Herisau, Degersheim, Wattwil and Ebnat-Kappel to Nesslau-Neu Sankt Johann in northeast Switzerland, and from Rapperswil via Seedamm, Pfäffikon SZ and Biberbrugg to Arth-Goldau in Central Switzerland.
In all, the SOB network measures 128.9 kilometres (80.1 miles), and comprises the following lines:
The Voralpen Express (VAE, Pre-Alpine Express), a named train, is jointly operated by the Südostbahn and the Swiss Federal Railways (SBB). It runs every hour as an InterRegio (IR) express train from Lucerne to St. Gallen via Arth-Goldau, Pfäffikon SZ, Rapperswil and Wattwil, continuing as a regional train to Romanshorn. SBB track is between Lucerne and Arth-Goldau, and between Rapperswil and Wattwil.