The Audi S8 is a high-performance version of the Audi A8, an executive car produced by German automaker Audi. It was introduced in 1998, four years after the A8's introduction to the European market. In 1998, Audi introduced the S8, a high-performance version of the Audi A8 in the vein of Mercedes-Benz AMG models.

Although it shared the standard model's platform, it featured a re-tuned, 340 PS (335 hp/250 kW) version of the standard V8 engine, a re-tuned suspension with larger wheels and upgraded tires, enlarged brakes and a re-calibrated version of the 5-speed Tiptronic transmission (European-spec. models had a 6-speed manual transmission option); quattro was standard. At the same time of the A8's 2001 facelift, the S8 received another 20 bhp (15 kW), taking the output of the engine to 360 bhp (270 kW). This was the first model to be introduced to the American market. Production of the first-generation S8 ended in 2003, shortly before the introduction of the second-generation D3-platform A8.