Breisgau-S-Bahn GmbH (BSB) was a regional railway operator in the German state of Baden-Württemberg.

It was a subsidiary of Südwestdeutsche Verkehrs-Aktiengesellschaft (SWEG), a transport company owned by the state of Baden-Württemberg.

[1] The company operated S-Bahn services over DB Netz AG-owned tracks in the area around Freiburg.

The services ran on short sections of the main line Rhine Valley Railway, together with the Elztalbahn and Breisachbahn branch lines.

This German rapid transit-related article is a stub.