Niall Mór O'Neill (Irish: Niall Mór Ó Néill) was a lord of Clandeboye in medieval Ireland. He succeeded his father, Conn O'Neill, to the lordship after his death in 1482. He reigned until his own death in 1512, after which he was succeeded by his son Hugh O'Neill. O'Neill's nickname Mór meant "great". O'Neill's chief residence was at Edenduffcarrick on the shore's of Lough Neagh in modern-day County Antrim, Northern Ireland. In his obituary in the Annals of the Four Masters it is stated that he did not pay homage to the O'Neill's of Tyrone, the O'Donnell's or the English.