In Pixar's Cars, the racing organization whose championship Lightning McQueen enters is the Piston Cup.
The Piston Cup is the fictional stock-car racing competition at the center of the first film. Lightning begins the story as a rookie contender fighting for the championship alongside veteran racer The King and aggressive rival Chick Hicks.
The film's opening and finale revolve around a three-way tie-breaker race after the competitors finish level on points. Lightning's ambition to win the Piston Cup initially causes him to overlook the people around him, but his experiences in Radiator Springs change his priorities.
The World Grand Prix belongs to Cars 2, not the first film's main championship. The Piston Cup is a fictional name created for the Cars universe and is not the same as a real-world racing series.