Shane O'Neill, head of the O'Neill dynasty in Ireland (born 1530)

Shane O'Neill was an Irish chieftain of the O'Neill dynasty of Ulster in the mid-16th century. Shane O'Neill's career was marked by his ambition to be the O'Neill—sovereign of the dominant O'Neill family of Tír Eoghain. This brought him into conflict with competing branches of the O'Neill family and with the English government in Ireland, who recognised a rival claim. Shane's support was considered worth gaining by the English even during the lifetime of his father Conn O'Neill, 1st Earl of Tyrone. But rejecting overtures from the 3rd Earl of Sussex, the lord deputy from 1556, Shane refused to help the English against the Scottish settlers on the coast of Antrim, allying himself for a short time instead with the MacDonnells, the most powerful of these settlers. Shane viewed the Scottish settlers as invaders, but decided to stay his hand against them with hopes of using them to strengthen his position with the English. However, tensions quickly boiled over and he declared war on the Scottish MacDonnell's defeating them at the Battle of Glentaisie despite the MacDonnells calling for reinforcements from Scotland. The Scottish MacDonnells would later assassinate Shane O'Neill and collect the bounty on his head.

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.