Which fictional racing series is contested in Pixar's Cars?

The fictional racing series contested in Pixar's Cars is the Piston Cup.

The Piston Cup is the main stock-car championship in the first film. Lightning McQueen is a rookie competing for the title when the story begins, and the film's ending centers on the final race and the consequences of a three-way championship situation.

The name is a playful reference to real-world motorsport trophies and engine terminology. The Piston Cup also gives the film a recognizable season structure, with sponsors, veteran drivers, pit crews, race officials, and championship standings.

The Piston Cup is different from the World Grand Prix in Cars 2, which is an international event created for that film. Dinoco is a sponsor associated with several racers, not the name of the racing series. These distinctions help separate the franchise's fictional competitions and commercial brands.