John Downes may refer to:
- John Downes (regicide) (1609–c. 1666), English commissioner convicted of regicide of Charles I of England at the restoration of Charles II
- John Downes (prompter) (died c. 1712), English theatre prompter for most of the Restoration period, 1660–1700
- John Downes (naval officer) (1786–1854), American Commodore and ship captain in the United States Navy
- John Downes (sailor) (1870–1943), British Olympic sailing gold medalist in 1908
- John K. Downes, Canadian politician, member of the Legislative Assembly of Manitoba, 1922–1927