John Duff (disambiguation)
John Duff (1895–1958) was a Canadian race car driver.
John Duff is also the name of:
- John Duff (counterfeiter) (1759–1799), American counterfeiter, hunter, and scout
- John Duff (UP), president of Union Pacific Railroad (1873–1874)
- John B. Duff (born 1931), former commissioner of The Chicago Public Library
- John Finlay Duff (1799–1868), was captain of ship Africaine and businessman in South Australia