The SM was Citroën's flagship vehicle, competing with other high-performance GTs of the time from manufacturers such as Jaguar, Lotus, Ferrari, Aston Martin, Alfa Romeo and Porsche. France had not had a production vehicle in this segment after World War II, except for the export oriented Chrysler V8 engine Facel Vega in the late 1950s.
The thriving French luxury car industry was decimated by post-World War II puissance fiscale regulation, which has hamstrung French manufacturers for decades.
Designed in-house by Citroën's chief designer Robert Opron, the SM bears a vague family resemblance to both the DS and the Maserati Mistral. Like the DS, the SM retains the rear-wheel spats, and seen from above, the SM resembles a teardrop, with a wide front track tapering to a narrower rear track.