O'DONNELL, the name of an ancient and powerful Irish family, lords of Tyrconnel in early times, and the chief rivals of the O'Neills in Ulster. Like the family of O'Neill (q.v.), that of O'Donnell was descended from Niall of the Nine Hostages, king of Ireland at the beginning of the 5th century; the O'Neills, or Cinel Owen, tracing their pedigree to Owen (Eoghan), and the O'Donnells, or Cinel Connell, to Conall Gulban, both sons of Niall. Tyrconnel, the district named after the Cinel Connell, where the O'Donnells held sway, comprised the greater part of the modern county of Donegal except the peninsula of Inishowen; and since it lay conterminous with the territory ruled by the O'Neills of Tyrone, who were continually attempting to assert their supremacy over it, the history of the O'Donnells is for the most part a record of tribal warfare with their powerful neigh bours, and of their own efforts to make good their claims to the overlordship of northern Connaught.
The first chieftain of mark in the family was Goffraidh (God frey), son of Donnell Mor O'Donnell (d. 1241). Goffraidh, who was "inaugurated" as "The O'Donnell," i.e., chief of the clan, in 1248, successfully raided Tyrone and Connaught, and was se verely wounded in the battle of Roscede (1257). In the following year he defeated Brian O'Neill, but died soon after from his old wounds. He was succeeded in the chieftainship by his brother Donnell Oge.
In the 16th century, when the English began to make deter mined efforts to bring the whole of Ireland under subjection to the Crown, the O'Donnells of Tyrconnel played a leading part, co operating at times with the English, especially when such co operation appeared to promise triumph over their ancient ene mies the O'Neills, at other times joining with the latter against the English authorities.