The Audi RS 6 quattro, commonly referred to as the RS6 ' is a mid-size sports-focused executive car, produced by the high-performance private subsidiary company quattro GmbH, for Audi AG, part of the Volkswagen Group. The first and second versions of the RS6 were produced as a five-door five-seat "Avant", Audi's name for an estate car–station wagon and a four-door five-seat saloon–sedan. The third generation is only available as an Avant.
The "RS" initials are taken from the German: RennSport – literally translated as "racing sport", and is Audi's ultimate 'top-tier' high-performance trim level, positioned a noticeable step above the "S" model specification level of Audi's regular model range line-up. Like all Audi "RS" models, the RS6 pioneers some of Audi's newest and most advanced engineering and technology, and so could be described as a halo vehicle, with the latest RS6 having the most powerful internal combustion engine out of all Audi models, with more horsepower and torque than the physically larger Audi S8. Unlike the A6 and S6, however, the RS6's engines in the C5 and C6 iterations have not been shared with any other vehicle in Audi's lineup. However, for the C7 generation, the Audi RS6 has the same 4.0L biturbo V8 engine as the Audi RS7, with both being positioned at the top of the Audi S and RS range, and detuned variants of the same engines are found in the Audi S8, Audi A8, and Audi S6. Based on the A6 platform, the RS6's internal combustion engines are front-mounted and longitudinally oriented, while the transmission is mounted immediately at the rear of the engine in a longitudinal orientation, in the form of a transaxle. Like all S and RS models, the RS6 is only available with Audi's 'trademark' Torsen-based quattro permanent four-wheel drive system. The C5 RS6 was the fourth model to come out of Audi's private subsidiary company, "quattro GmbH". The first was the Audi RS2 Avant, from a joint venture between Porsche and quattro GmbH for the Audi marque. The second was the Audi C4 S6 Plus, produced from April 1996 to July 1997. Third was the 2000 Audi B5 RS4; the fifth was the 2005 Audi B7 A4 DTM Edition saloon, and the sixth was the 2006 Audi B7 RS4. The seventh and current (as of January 2010) quattro GmbH model is the latest Audi C6 RS 6. Production of the original Audi C5 RS 6 began in June 2002 and ended in September 2004. The second and current Audi C6 RS 6 was introduced at the 2007 Frankfurt Motor Show. The original RS6 was the first Audi RS model exported to North America, while the succeeding C6 RS6 is only sold in Europe.