S-Bahn Mitteldeutschland represents an enlargement of the previous Leipzig-Halle S-Bahn. It is an electric rail public transit system operating in the metropolitan area of Leipzig-Halle, Germany. This S-Bahn network developed from two separate S-Bahn networks of Halle (Saale) and Leipzig, which were established separately in 1969 and then linked in 2004. With the opening of the Leipzig City Tunnel on 15 December 2013 as a new artery, the network was extended for the first time to the federal states of Thuringia and Brandenburg. With a system length of 802 km (498 mi), it is the largest S-Bahn network in Germany, displacing the long-time title holder Rhine-Ruhr S-Bahn from that position. The locomotive-hauled double-decker trains partly dating back to the DDR-era have been largely replaced by electric multiple unit Bombardier Talent 2 trains, but some older trains are still used during rush hour.

The S-Bahn is a hybrid urban-suburban rail system serving a metropolitan region predominantly in German-speaking countries. Some of the larger S-Bahn systems provide service similar to rapid transit systems, while smaller ones often resemble commuter or even regional rail systems. The name S-Bahn derives from Schnellbahn, Stadtbahn or Stadtschnellbahn.