Audi RS4/S4

The Audi RS 4 quattro is the top tier and highest performing version of some specific generations of the Audi A4 range of automobiles. It is a sports-focused compact executive car (often called sport compact in some countries), produced by Audi's high-performance private subsidiary quattro GmbH, in limited numbers, for German car manufacturer AUDI AG, part of the larger Volkswagen Group.

The Audi S4 is the high performance variant of Audi's compact executive car A4. The original Audi S4, built from 1991 until 1994, was a performance-oriented version of Audi's 100 saloon/sedan. All subsequent S4s since 1997 have been based on the Audi A4; and as the A4 has evolved from one generation to the next, so has the S4.