Callaghan O'Callaghan •
Barry O'Callaghan (born 1969): CEO of Riverdeep Interactive Learning •
Bill O'Callaghan (1868–1946): Irish hurler •
Billy O'Callaghan (born 1974): Irish novelist and short-story writer •
Cian O'Callaghan (born 1979) : politician, Irish Social Democrats •
Con O'Callaghan (decathlete) (1908–1976): Ireland's first Olympic decathlete; brother of
Pat O'Callaghan •
David O'Callaghan (dual player) (born 1983) •
David O'Callaghan (Kerry Gaelic footballer) (born 1987) •
Denis O'Callaghan (born 1949): Australian rules footballer •
Donncha O'Callaghan (born 1979): Irish international rugby union player •
Edmund Bailey O'Callaghan (1797–1880): doctor, journalist, and leader of political movements in Ireland and Quebec •
Gareth O'Callaghan (born 1961): Irish broadcaster & Author •
Gary O'Callaghan, (1933–2017): Australian radio announcer •
George O'Callaghan Irish footballer •
George O'Callaghan-Westropp (1864–1944): Irish landowner and politician •
George O'Callaghan, 2nd Viscount Lismore (1815 – 1898) Irish peer and British Army officer •
Geraldine O'Callaghan: kickboxer •
Jim O'Callaghan (born 1968): Irish Fianna Fáil politician •
John O'Callaghan (Medal of Honor) (1850–1899): American soldier and Medal of Honor recipient •
John O'Callaghan: Irish musician and DJ •
José O'Callaghan Martínez (1922–2001): Spanish Jesuit, papyrologist and Biblical scholar •
Joseph O'Callaghan (1824–1869): American Jesuit educator •
Joseph T. O'Callahan (1905–1964): Captain, US Navy, Jesuit priest, Medal of Honor recipient •
Kevin O'Callaghan Irish footballer •
Kilian O'Callaghan (born 1963): ballet dancer and teacher, from Monkstown, Co. Cork •
Leland James O'Callaghan (1915–1997): American businessman and politician from Georgia • Miriam O'Callaghan (camogie): 26th president of the Camogie Association •
Miriam O'Callaghan (media personality) (born 1957): Irish television current affairs presenter with RTÉ •
Mollie O'Callaghan Australian Olympic Swimming Gold Medallist •
Pat O'Callaghan (1906–1991): first Irish athlete to win an Olympic medal •
Robert O'Callaghan (British Army officer) (1777–1840):
British Army officer and politician •
R. E. O'Callaghan (1855–1936): English vegetarianism activist, lecturer and writer •
Seán O'Callaghan (1954–2017): IRA informer from Tralee, County Kerry •
Sian O'Callaghan (1988–2011): murder victim from Swindon, Wiltshire, UK •
Therése O'Callaghan: camogie player captain ==Places==