O'Hanlon is an Irish surname associated with the Ó hAnluain sept. As with other similar names, the added prefix "O'" means "son of" (Hanlon).
Notable people with that surname include:
Ardal O'Hanlon, Irish comedian
Bill O'Hanlon, American psychologist
Evan O'Hanlon, Australian Paralympian
Fergal O'Hanlon, Irish Republican Army member
George O'Hanlon, American actor
John O'Hanlon (chess player) (1876–1960), Irish chess master
John O'Hanlon (Lackaghmore) (1889–1920), Sinn Féin member shot during the Irish War of Independence
John O'Hanlon (politician) (1872–1956), Irish politician and journalist
John O'Hanlon (writer) (1821–1905), Irish priest and writer
Michael E. O'Hanlon (born 1961), American policy consultant
Michael F. O'Hanlon (1890–1967), Irish politician
Paddy O'Hanlon (1944–2009), Irish politician
Pat O'Hanlon, (born 1991), Australian Rugby League player
Redmond O'Hanlon, a British writer
Redmond O'Hanlon (outlaw), a 17th-century Irish guerrilla soldier
Rory O'Hanlon, an Irish politician
Sean O'Hanlon, an English footballer
Siobhán O'Hanlon, Sinn Féin politician, former Provisional IRA
Virginia O'Hanlon, catalyst for "Yes, Virginia, there is a Santa Claus"