The Audi A8 is a four-door, full-size, luxury sedan car manufactured and marketed by the German automaker Audisince 1994. Succeeding the Audi V8, and now in its third generation, the A8 has been offered with both front- or permanent all-wheel drive—and in short- and long-wheelbase variants. The first two generations employed the Volkswagen Group D platform, with the current generation deriving from the MLB platform. After the original model's 1994 release, Audi released the second generation in late 2002, and the third and current iteration in late 2009.

Notable for being the first mass-market car with an aluminium chassis, all A8 models have utilised this construction method co-developed with Alcoa and marketed as the Audi Space Frame.

A mechanically-upgraded, high-performance version of the A8 debuted in 1996 as the Audi S8. Produced exclusively at Audi's Neckarsulm plant, unlike the donor A8 model, the S8 has been available only in short-wheelbase form and is fitted standard with Audi's quattro all-wheel drive system.