- Source: John Duff (disambiguation)
John Duff (1895–1958) was a Canadian race car driver.
John Duff may also refer to:
John Duff (counterfeiter) (1759–1799), American counterfeiter, hunter, and scout
John Duff (singer) (born 1988), American pop singer
John B. Duff (born 1931), former commissioner of The Chicago Public Library
John Finlay Duff (1799–1868), captain of ship Africaine and businessman in South Australia
John Wight Duff (1866–1944), Scottish classicist and academic