John Kelly or Jack Kelly is the name of:

• John Kelly of Killanne (died 1798), leader of the Irish Rebellion of 1798 in Wexford
• John Kelly (U.S. politician) (1822–1886), politician in Tammany Hall, U.S. Representative from New York (1855–1858)
• Sir John Kelly (1871–1936), British Admiral of the Fleet
• John D. Kelly (1928-1952), USMC, Korean War Medal of Honor recipient
• John J. Kelly (1898–1957), USMC, World War I Army and Navy Medal of Honor recipient
• John J.H. Kelly b. 1851 d. February 4, 1907. Medal of Honor, Indian Campaign
• John Larry Kelly, Jr (1923–1965), originator of the Kelly criterion
• Jack Kelly (actor) (1927–1992), American film and television actor
• John M. Kelly (politician) (1931–1991), Irish Fine Gael politician and cabinet member
• John P. Kelly (Philadelphia) (born c. 1939), Philadelphia councilman
• John P. Kelly (New Jersey), member of the Board of Chosen Freeholders, Ocean County, New Jersey

• John Kelly (fiddler)
• John Kelly (author)
• John Kelly (Doctor Who) of the Doctor Who Restoration Team
• John Kelly (health planner), RKW
• John Kelly (musician), a vocalist with the band Horslypse
• John Kelly (broadcaster), an ice hockey sportscaster
• John Kelly (judge), Australian judge

Sportspersons

• John B. Kelly (disambiguation), father and son United States rowers
  • John B. Kelly, Sr. (1889–1960), triple gold medal winning Olympic rower, father of Grace Kelly and John B. Kelly, Jr.
  • John B. Kelly, Jr. (1927–1985), Olympic rower, Philadelphia councilman, head of the US Olympic Committee and brother of Grace Kelly
• John Kelly (sportsman), nicknamed "Honest John", a baseball player and umpire, boxing referee and gambling operator
• John Kelly (rugby player)