The Audi S4 is a high performance sport version of the popular Audi A4. The S4 name was originally used for the sport version of the Audi 100. Audi was re-configuring its lineup during the early 1990s, and introduced the S4 in 1991 as the performance version of the re-styled 100 sedan. Despite being based on the C4 Platform and sharing its basic structure with the 100, the S4 effectively took the place of the 200 Turbo Quattro,

which had been discontinued the year before. Being the first in the S4 lineup, it is commonly referred to as the UrS4, coming from the German words Ursprünglich (original). The S4 was sold worldwide with a turbocharged version of Audi's 2.2 L (2226 cc), 20-valve inline-5 engine developing 230 PS (227 hp/169 kW) and 350 Nm (258 ft·lbf) of torque. A 280 PS (276 hp/206 kW) 4.2 L V8 became available to European customers as an option. quattro all-wheel-drive and a manual transmission (five and six-speed in Europe, five-speed only in North America) were standard equipment, although a 4-speed automatic transmission was available as an option. The most common configuration 2.2 L 6-speed offered good acceleration for its day, achieving 100 km/h (62 mph) in just 6.2 seconds. After Audi dropped the 100 nameplate and re-badged the car as A6 in 1994, the S4 became the S6, although the only real changes to the model were minor cosmetic updates and the addition of a more powerful S6 Plus model to the lineup again using the V8 engine. After the first generation A6 was replaced in 1997 by an updated version based on C5 Chassis, the S4 and S6 became distinctly separate from one another.