John O'Mahony (disambiguation)
John O'Mahony was founder of the Irish Republican Brotherhood.
John O'Mahony may also refer to:
- John O'Mahony (Mayo politician), Irish Fine Gael politician and manager of the Galway Football Team
- John O'Mahony (Gaelic footballer), Irish retired Gaelic footballer
- John O'Mahony (Australian footballer), Australian footballer for Hawthorn
- John O'Mahony (antiquarian), Irish Catholic priest and founder of the Cork Historical and Archaeological Society
- Sean Matgamna, also known as John O'Mahony, Trotskyist theorist
- Seán O'Mahony, Sinn Féin politician who represented the South Fermanagh constituency
- John O Mahoney, Irish Gaelic footballer