The Piston Cup is the fictional championship race central to Pixar's Cars.
Lightning McQueen is a rookie competitor in the Piston Cup season, and the film's opening conflict begins when a three-way tie leads to a final race in California. McQueen's ambition to win the championship drives his journey before his unexpected stay in Radiator Springs changes his priorities.
The Piston Cup is modeled broadly on stock-car racing, especially the visual language of NASCAR. It is represented through speedways, pit crews, sponsors, and highly competitive drivers rather than through a real-world championship name.
The Piston Cup should not be confused with the Dinoco brand, which is a sponsor, or the World Grand Prix, the international competition featured in Cars 2. Those names belong to different parts of the fictional racing world.