Murtagh Dulenagh O'Neill (Irish: Muirchertach Duileanach Ó Néill) was a lord of Clandeboye in medieval Ireland.
[1] His hold over Clandeboye was gradually weakened by his nephews, the sons of Niall Oge and Phelim Bacagh O'Neill.
[1] O'Neill died after 1556, however as a sign of how far his stock had fallen his death was not recorded.
[1] His epithet of Duileanach suggests that he may have been fostered by the O'Doolan's found in what is now the barony of Castlereagh, which was within the Clandeboy domain.
[2] Another son, Hugh (Aodh Buidhe), along with his family retained some land until the seventeenth-century around Toome in south-west modern-day County Antrim, Northern Ireland.