The Questor Grand Prix was a non-championship race for Formula One and Formula 5000 cars held on 28 March 1971 to inaugurate a new racing facility in California, the Ontario Motor Speedway, built by the Questor conglomerate.

Because of the smaller fuel tanks of the F5000 cars, the race was run in two heats of 32 laps, and the final result decided by a points system.

Jackie Stewart qualified on pole for Heat 1 and finished runner-up behind Mario Andretti.

[1] Hopes for a regular fixture rapidly faded due to financial problems.

The Questor Grand Prix remained a one-off event and the Ontario Motor Speedway was never again used to host a Formula One race.