The Mercedes-Benz W125 was a Grand Prix racing car designed by Rudolf Uhlenhaut to race during the 1937 Grand Prix Racing season. The car was used by Rudolf Caracciola to win the 1937 European Championship and W125 drivers also finished in the second, third and fourth positions in the championship. In fact, the brilliant driving of Caracciola, Seaman, Lang and von Brauchitsch, brought almost complete triumph throughout the 1937 season.
In the W125, Mercedes-Benz had created a car which was a generation ahead of its peers. The supercharged engine, with 8 cylinders in line (94.0 x 102.mm) and 5,662.85 cc (345.56 CID), attained an output of up to 595 horsepower (444 kW) in race trim. The W125 was considered the most powerful road racing car ever for three decades until large capacity American-built V8 engines in CanAm sports cars reached similar power in the late 1960s. In Grand Prix racing itself, the figure was not exceeded until the early 1980s (when Grand Prix racing had become known as Formula One), with the appearance of turbo-charged engines.