The C-1 is a rail service of Cercanías Madrid commuter rail network, operated by Renfe Operadora. It runs from Príncipe Pío station in western Madrid to Madrid Barajas Airport Terminal 4, through the city center of Madrid. The C-1 shares tracks for the majority of its length with services C-7 and C-10 while it also shares large parts with C-2, and C-8. The service has existed in its current form since 2011, when it opened.

Cercanías Madrid is the commuter rail service that serves Madrid, the capital of Spain, and its metropolitan area. It is operated by Cercanías Renfe, the commuter rail division of Renfe, the former monopoly of rail services in Spain. Its total length is 370 km.