John O'Connor may refer to:

• John O'Connor (Archdeacon of Emly) (fl. 1854–1904), Archdeacon of Emly, 1880–1904
• John J. O'Connor (bishop of Newark) (1855–1927), Roman Catholic Bishop of Newark
• John O'Connor (priest) (1870–1952), British Roman Catholic priest, model for the fictional detective Father Brown
• John O'Connor (cardinal) (1920–2000), Roman Catholic Archbishop of New York

• John O'Connor (Canadian politician) (1824–1887)
• John O'Connor (Lord Mayor of Dublin) (c. 1835–1891), Lord Mayor of Dublin and MP for South Kerry
• John O'Connor (North Kildare MP) (1850–1928)
• John O'Connor (Australian politician) (1878–1937), member of the South Australian House of Assembly
• John J. O'Connor (New York representative) (1885–1960), US Representative from New York
• John J. O'Connor (Brooklyn politician) (1855–1898), member of the New York State Assembly
• John M. O'Connor (born 1954), Attorney General of Oklahoma
• John S. O'Connor (1896–1967), Irish politician

• John O'Connor (English cricketer) (1867–1936)
• John O'Connor (Australian cricketer) (1868–1952)
• John O'Connor (Cork hurler) (fl. 1890s)
• John O'Connor (athlete) (1893–1977), Irish Olympic athlete
• John C. O'Connor (1878–1922), American college football coach
• Johnny O'Connor (baseball) (1891–1982), Major League Baseball player
• Johnny O'Connor (hurler) (1928–2010), Irish hurler who played for Waterford
• John O'Connor (Wexford hurler) (born 1965), Irish hurler who played for Wexford
• Johnny O'Connor (born 1980), Irish rugby union player

• John O'Connor (musician) (born 1949), British guitarist, television composer and recording artist
• John O'Connor (painter) (1830–1889), Irish painter
• John Carroll O'Connor, birth name of American actor Carroll O'Connor (1924–2001)
• John Jay O'Connor (1930–2009), American lawyer and husband of United States Supreme Court Justice Sandra Day O'Connor
• John J. O'Connor (artist) (born 1972), American artist
• John J. O'Connor (historian) (1904–1978), American historian and sociologist
• John J. O'Connor (journalist) (1933–2009), American journalist and critic
• John J. O'Connor (mathematician) (fl. 1990s–2010s), owner of MacTutor History of Mathematics archive
• John Kennedy O'Connor (born 1964), television and radio broadcaster

• John Conner (disambiguation)
• John Connor (disambiguation)
• Jack O'Connor (disambiguation)
• John O'Conor (born 1947), Irish pianist
• Jon O'Connor (born 1976), English footballer
• John O'Connor Power (1846–1919), Irish politician
• "He'd Have to Get Under – Get Out and Get Under (to Fix Up His Automobile)", a song also known as "Johnny O'Connor"