The Alfa Romeo P3, P3 monoposto or Tipo B was a classic Grand Prix car designed by Vittorio Jano, one of the Alfa Romeo 8C models. The P3 was first genuine single-seat Grand Prix racing car and Alfa Romeo's second monoposto after Tipo A monoposto (1931). It was based on the earlier successful Alfa Romeo P2. Taking lessons learned from that car, Jano went back to the drawing board to design a car that could last longer race distances. The P3 was the first genuine single seater racing car, and was powered by a supercharged eight-cylinder engine. The car was very light for the period, weighing just over 1,500 lb (680 kg) despite using a cast iron engine block.