John William Mahler (November 16, 1936 – February 6, 2024) was an American open wheel race car driver in the USAC and CART Championship Car series.

John William Mahler was born in Alpha, Iowa, on November 16, 1936. He raced in the 1970–1973 and 1976–1981 seasons, with 39 combined career starts, including the 1972 and 1977–1979 Indianapolis 500. Mahler finished in the top ten six times, with his best finish in 6th position in 1970 at the Indianapolis Raceway Park road course.

Mahler qualified for the 1971 Indianapolis 500 but was replaced by his teammate who did not qualify, Dick Simon, due to sponsorship commitments. Mahler was presented with the American Auto Racing Writers and Broadcasters Association Jigger Award for the driver with the most hard luck. He was a member of the 1977 and 1979 Last Row Party for earning a position in the 11th and final row of the starting grid.

Mahler latterly owned and operated Classic Concrete Designs in Kansas City, Missouri. He died from cancer on February 6, 2024, at the age of 87.^[1]