In the fourteenth century a branch of the Tir Eoghain O'Neills migrated eastwards and, under the leadership of Aodh Buidhe ("Yellow Hugh"), wrested large areas of Antrim and Down from Norman control. The territory at the centre of their power, Clandeboy, took its name from them (Clann Aodh Buidhe),and they in turn became known as the Clandeboye O'Neills. Their principal castle was at Edenduffcarrig, northwest of Antrim town, still occupied by an O'Neill. The present titular head of this branch of the family is Hugo O'Neill, "O'Neill of Clandeboy", a Portuguese businessman descended from Muircheartach, chief of the family from 1548 to 1552.
The descent of the original Tyrone family has also continued unbroken, down to the present holder of the title of O Neill Mor, Don Carlos O'Neill of Seville, who also holds the Spanish titles of Marques de la Granja, Marques del Norte and Conde de Banajir. He is descended, through the O'Neills of the Fews in Co. Armagh, from Aodh, second son of Eoghan, inaugurated as chief of the name in 1432.
Dramatist Eugene O?Neill (1888-1953) winner of the 1936 Nobel Prize for Literature, was the son of an emigrant from Co. Kilkenny. Conflicts with his family and cultural heritage formed the basis of much of his work.
Superintendent Francis O?Neill (1848-1936) of the Chicago Police, originally from Bantry, is renowned in traditional music circles for the enormous collection of melodies he published in 1903, Music of Ireland - 1850 Melodies: Airs, Jigs, Reels, Hornpipes, Long Dances, Marches etc. ...
Terence O?Neill (1912-90) was Prime Minister of Northern Ireland from 1963 until his resignation in 1969. His efforts at reform failed to prevent the violence which continued up to the Belfast Agreement of 1998.