A fastback is an automotive styling feature, defined by the rear of the car having a single slope from the roof to the tail.[3][4] The kammback is a type of fastback style.

1935 Stout Scarab

1949 Cadillac Series 62 rear

1950s Warszawa M20

1956 Porsche 356A

1967 AMC Marlin, a full-size 2-door fastback[1]

1968 Ford Mustang, a pony car fastback[2]

1978 Citroën CX 4-door fastback sedan

2006 Mercedes-Benz CLS55 AMG

Unlike the Tesla Model S 5-door liftback, the Tesla Model 3 seen here is a 4-door fastback sedan with a separate trunk.

Some models, such as the Ford Mustang, have been specifically marketed as fastbacks, often to differentiate them from other body styles (e.g. coupe models) in the same model range. The 4-door coupe is a common branding term used today to describe fastback sedans.

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A fastback is often defined as having a single slope from the roof to the rear of the vehicle.[5]

This 1974 Leyland P76 can be considered both a fastback (with a single uninterrupted slope from the roofline to the rear) and a liftback (with a tailgate hinged at the roof).

A fastback trunk lid with a fixed rear window (1965 Rambler Marlin fastback)

The term “fastback” is not interchangeable with “liftback“; the former describes the shape of the car, and the latter refers to a roof-hinged tailgate that lifts more upwards than rearwards.

More specifically, Road & Track have defined the fastback as

A closed body style, usually a coupe but sometimes a sedan, with a roof sloped gradually in an unbroken line from the windshield to the rear edge of the car. A fastback naturally lends itself to a hatchback configuration and many have it, but not all hatchbacks are fastbacks and vice versa.[6]

In the case of the Ford Mustang, the term “fastback” is used to differentiate against the coupénotchback body style,[7][8] which has a steeper rear window followed by a horizontal trunk lid.

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