Owen Roe O'Neill was a Gaelic Irish soldier and one of the most famous of the O'Neill dynasty of Ulster. O'Neill left Ireland at a young age and spent most of his life as a mercenary in the Spanish Army serving against the Dutch in Flanders during the Eighty Years' War. After the Irish Rebellion of 1641, O'Neill returned and took command of the Irish Confederate Ulster Army. He is known for his victory at the Battle of Benburb in 1646.

The O'Neill dynasty are a lineage of Irish Gaelic origin that held prominent positions and titles in Ireland and elsewhere. As kings of Cenél nEógain, they were historically one of the most prominent family of the Northern Uí Néill, along with the O'Donnell dynasty. Some O'Neills state that their ancestors were kings of Ailech during the Early Middle Ages, as descendants of Niall of the Nine Hostages.