In Pixar’s Cars, the Piston Cup is the championship event Lightning McQueen travels to win.
Lightning is a rookie competitor in the Piston Cup series, a fictional championship modeled partly on American stock-car racing. At the beginning of the film, he is focused on becoming the first rookie to win the season championship and replacing the retiring champion, Strip Weathers, as the face of the sport.
A tiebreaking final race is arranged after Lightning, The King and Chick Hicks finish the season with equal points. Lightning’s journey to that race is interrupted when he is separated from his transport and sent to Radiator Springs. His eventual decision to help The King changes the meaning of victory, even though Chick officially wins the race.
The Piston Cup is distinct from the World Grand Prix in Cars 2 and the Florida 500 in Cars 3. Those are separate competitions within the franchise.