The Audi S8 is a full-size luxury car of the Audi S models produced by the German automaker Audi AG, manufactured by Audi Sport GmbH at the Neckarsulm plant. The S8 is the mechanically-upgraded, high-performance version of the Audi A8, fitted standard with Audi's quattro all-wheel drive system, and was only offered with a short-wheelbase for the first three generations, being joined by a long-wheelbase variant option for the fourth generation.

(D2) First generation

Audi S8 (D2) was produced from 1996 to 2003. The car featured a 4.2 liter V8 with 340 PS. The D2 S8 could accelerate from 0–60 mph in 6.2 seconds. It has a curb weight of 1730 kg. In 1999, the car was updated with a power increase to 369 PS, which brought the 0–60 mph acceleration down to 5.6 seconds. Top speed was electronically limited to 155 mph. It has a curb weight of 1845 kg. An Audi S8 (D2) was chosen as the car of the protagonists of the film Ronin.

(D3) Second generation

Audi S8 (D3) was released from 2006 to 2010. The car was equipped with a modified V10 engine shared with the Lamborghini Gallardo of the same years. It produces 450 PS, detuned by 50 PS from the Gallardo's power output of 500 PS with the purpose of increasing its fuel efficiency. The top speed is electronically limited to 155 mph. Acceleration from 0–60 mph takes 5.1 seconds. It has a curb weight of 1940 kg.

(D4) Third generation

Audi S8 (D4) (2012–2015, facelift 2015–2018) 3,993 V8 TFSI. It produces 520 PS. It accelerates from 0-60 mph in 3.6 seconds, bests the quarter mile in 11.9 seconds at 118 mph and reaches a top speed of 155 mph. Curb weight is 2050-2065 kg.

(D5) Fourth generation

The release of the fourth generation S8 was planned to begin in 2019–2020. For the first time, it was to be offered in both short and long-wheelbase versions, with the long-wheelbase S8 (i.e., an S8L) being the sole variant offered in North America. The S8 is now the flagship of the Audi A8 range, since the nominally higher-end A8 L W12 was no longer offered after the 2018 model year. The Audi S8 (D5) features 563 hp and 590 lbft of torque as a result of its 4.0-liter twin-turbo V8. A 48-volt mild hybrid system will allow for stop-start use and coasting. Compared to the S8 plus (D4), the S8 (D5) has 34 hp less but 37 lbft more torque.