John O'Mahony (disambiguation)

John O'Mahony (1816–1877) was founder of the Irish Republican Brotherhood.

John O'Mahony may also refer to:
 * John O'Mahony (Mayo politician) (1953–2024), Irish Fine Gael politician who represented Mayo and twice an All-Ireland winner managing the Galway Football Team
 * John O'Mahony (Gaelic footballer) (born 1937), Irish retired Gaelic footballer
 * John O'Mahony (Australian footballer) (born 1931), Australian footballer for Hawthorn
 * Sean Matgamna (born 1941), also known as John O'Mahony, Trotskyist theorist
 * Seán O'Mahony (1864–1934), Sinn Féin politician who represented the South Fermanagh constituency
 * John O Mahoney, Irish Gaelic footballer