The Citroën GS is a front-engine, front-drive, four or five door, five passenger family car manufactured and marketed by Citroën in two series: for model years 1970–1979 in fastback saloon and estate bodystyles and subsequently as the GSA for model years 1980–1986 in hatchback and estate body styles – the latter after a facelift. Combined production reached approximately 2.5 million.

The C-segment is the 3rd category of the European segments for passenger cars and is described as "medium cars". It is equivalent to the Euro NCAP "small family car" size class, and the compact car category in the United States.