Ó Ceallacháin,[1] primarily anglicised O'Callaghan as well as variants of Callihan, is an Irish surname. Notable people with the surname include:
- Pat O'Callaghan (1906–1991), Irish hammer-thrower
- Seán Óg Ó Ceallacháin (1923–2013), journalist, author and broadcaster
- Bill Callihan (1916–1986), American football player
- Mike Callihan (b. 1947), Lieutenant Governor of Colorado
- Ryan Callahan, American hockey player
- Shane Callahan (b. 1995), American actor