Biography Wikipedia
Wikipedia:
John O'Callaghan may refer to:
John O'Callaghan (hurler) (born 1988), Irish hurlerJohn O'Callaghan (DJ), Irish DJJohn O'Callaghan (politician), secretary of the United Irish LeagueLiam McCarthy and John D. O'Callaghan, BT Young Scientists of the Year and EU Young Scientists of the Year, 2009John O'Callaghan (Medal of Honor recipient) (fl. 1868–1870), American soldier and Medal of Honor recipientJohn O'Callaghan (vocalist and guitarist of the American band, THE MAINE)