A fastback is a car body style whose roofline slopes continuously down at the back. The word can also designate the car itself. The style is seen on two-door coupés as well as four-door sedans.

Automobile designs that were ahead of their time when exhibited during the early 1930s included "teardrop streamlining at the rear, similar to what would become known as 'fastback' 25 years later." 'Fastback' was first recognized as a definition by Merriam-Webster in 1954, many years before the term 'hatchback' was popularized and entered the dictionary in 1970. Opinions vary as to whether the terms are mutually exclusive.

A contributor to an automotive-interest website singles out the unusual Stout Scarab from the early 1930s as "1ossibly the epitome of the early fastback definition". The Packard 1106 Twelve Aero Sport Coupe, introduced in 1933, is cited elsewhere as a fastback that foreshadowed trends which continued into the 1940s.

Early European fastback automobiles include: Bugatti Type 57 Atlantic, Porsche 356, Saab 92/96, Standard Vanguard, GAZ-M20 Pobeda, and Bentley Continental R-Type.

Numerous fastbacks were also made in America, where the style was previously called "torpedo back". They included Cadillac's Series 61 and 62 Club Coupes as well as various models from General Motors, Ford, and Chrysler.

At a 2007 U.S. car show, entries from the mid-1930s to the mid-1950s in a class called "Fabulous Fastbacks" included Nash Ambassador, Buick Roadmaster and Hudson Commodore models.Clements, Rob. "EyesOn Design 2007," Report and images for Ultimatecarpage.com, retrieved on August 14, 2008.

At a 2007 concours d'élégance in England, a similarly-named class for 1950s cars attracted examples from Maserati, Lancia, Fiat and Ferrari.

Aerodynamic advantages

Fastbacks provide an advantage in developing aerodynamic vehicles with a low drag coefficient. The Kamm tail is a related concept.

The trend towards a more steeply raked rear window on traditional "three-box" sedans blurs the distinction between fastback and notchback designs. The current Lexus LS460 exemplifies the trend.fact: date=August 2008 However, the roof of a true fastback design slopes down continuously to the rear, most often to the base of the trunk at the rear bumper. There is no distinct change of angle to a rear deck, whereas most four-door cars with steeply raked rear windows have less angled trunk lids; also high tails to maximize cargo space.

In 2008, the fastback design appeared on a concept car that almost defies categorization, the Chrysler ecoVoyager, that "Jack Telnack, former design chief for the Ford Motor Company, declared, 'It's a fastback van.'"Patton, Phil. "Looking at the Slope of Things to Come," The New York Times, January 20, 2008, retrieved on August 14, 2008. New types of crossover vehicles and different body proportions made possible by technological advances and new powerplants, are changing the shape of automobiles. Traditional nomenclature describing distinct vehicle bodies, such as the three-box sedan (engine compartment, passenger cabin and trunk) will vanish.