The Auto Union Grand Prix racing cars types A to D were developed and built by a specialist racing department of Auto Union's Horch works in Zwickau, Germany, between 1933 and 1939.
Early cars had V16 engines, later replaced by V12s that developed almost 550 horsepower. Wheelspin could be induced at over 100 mph (160 km/h), and the marked oversteer that persisted throughout the cars' development made all Auto Unions difficult to handle.
Between 1935 and 1937 Auto Unions won 25 races, driven by Ernst von Delius, Tazio Nuvolari, Bernd Rosemeyer, Hans Stuck and Achille Varzi. Their main competition came from the Mercedes Benz team, with Auto Union proving particularly successful in the 1936 and 1937 seasons. Known as the Silver Arrows, the cars of the two German teams dominated Grand Prix racing until the outbreak of World War II in 1939.