The Mercedes-Benz W125 was a Grand Prix racing car produced by German auto manufacturer Mercedes-Benz to race during the 1937 Grand Prix season. Designed by head designer Rudolf Uhlenhaut, 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.

Otto Wilhelm Rudolf Caracciola was a German racing driver. He won the European Drivers' Championship, the pre-1950 equivalent of the modern Formula One World Championship, an unsurpassed three times. He also won the European Hillclimbing Championship three times – twice in sports cars, and once in Grand Prix cars. Caracciola raced for Mercedes-Benz during their original dominating Silver Arrows period, named after the silver colour of the cars, and set speed records for the firm. He was affectionately dubbed Caratsch by the German public, and was known by the title of Regenmeister, or "Rainmaster", for his prowess in wet conditions.