The fictional championship series contested by Lightning McQueen in Pixar's Cars is the Piston Cup.
The Piston Cup is the main stock-car racing championship in the first film. McQueen is a rookie driver competing for the title when the story begins, and the film's opening race shows him tied with veteran racer The King and Chick Hicks before the decisive finale.
The championship is named after a piston-shaped trophy and is presented as the dominant racing competition in the film's version of the United States. It is not a real-world NASCAR title, although the races, cars, commentators, sponsors, and track culture draw heavily from American stock-car racing.
The Piston Cup also becomes part of McQueen's identity in later stories. In Cars 3, his struggle is tied to a changing generation of Piston Cup racers, especially the technologically advanced Jackson Storm. The World Grand Prix in Cars 2 is a separate international event.