DSB, an abbreviation of Danske Statsbaner, is the largest Danish train operating company, and the largest in Scandinavia. While DSB is responsible for passenger train operation on most of the Danish railways, goods transport and railway maintenance are outside its scope. DSB runs a commuter rail system, called the S-train, in the area around the Danish capital, Copenhagen, that connects the different areas and suburbs in the greater metropolitan area. Between 2010 and 2017, DSB operated trains in Sweden.

The Copenhagen S-train, the S-train of Copenhagen, Denmark, is a key part of public transport in the city. It is a hybrid urban-suburban rail serving most of the Copenhagen urban area, and is analogous to the S-Bahn systems of Berlin, Vienna and Hamburg. The trains connect the Copenhagen inner city with Hillerød, Klampenborg, Frederikssund, Farum, Høje-Taastrup and Køge. There are 170 km (110 mi) of double track with 87 S-train stations, of which eight are in neighbouring towns outside greater Copenhagen.