This king had fourteen sons, one of whom was Eoghan (Owen), from whom the O'Neills of the later history were descended.
Niall of the black knee), one of the most famous of the early Irish kings, from whom the family surname of the O'Neills was derived.
It was probably his son or nephew (for the relationship is uncertain, the genealogies of the O'Neills being rendered obscure by the contemporaneous occurrence of the same name in different branches of the family) Hugh O'Neill, lord of Tyrone, who was styled "Head of the liberality and valour of the Irish."
Contemporary with him was Neill Mor O'Neill (see below), lord of Clanaboy, from whose son Brian was descended the branch of the O'Neills who, settling in Portugal in the 18th century, became prominent among the Portuguese nobility, and who at the present day are the representatives in the male line of the ancient Irish kings of the house of O'Neill.
Conn O'Neill (c. 1480-1559), 1st earl of Tyrone, surnamed Bacach (the Lame), grandson of Henry O'Neill mentioned above, was the first of the O'Neills whom the attempts of the English in the 16th century to subjugate Ireland brought to the front as leaders of the native Irish.
Conn, who was related through his mother with the earl of Kildare (Fitzgerald), became chief of the Tyrone branch of the O'Neills (Cinel Eoghain) about 1520.
A stone inauguration chair of the O'Neills is preserved in the Belfast Museum.
In spite of the traditional enmity between the O'Neills and the O'Donnells, Tyrone allied himself with Hugh Roe O'Donnell, nephew of Shane's former enemy Calvagh O'Donnell, and the two chieftains opened communications with Philip II.
Owen Roe O'Neill (c. 1590-1649), one of the most celebrated of the O'Neills, the subject of the well-known ballad "The Lament for Owen Roe," was the son of Art O'Neill, a younger brother of Hugh, 2nd earl of Tyrone.
The Clanaboy (or Clandeboye) branch of the O'Neills descended from the ancient kings through Neill Mor O'Neill, lord of Clanaboy in the time of Henry VIII., ancestor (as mentioned above) of the Portuguese O'Neills.
In the 18th century the commanding importance of the O'Neills in Irish history had come to an end.
For the O'Neills of the 18th century, and especially the 1st Viscount O'Neill, see The Charlemont Papers, and F.
The O'Neills of Ulster: Their History and Genealogy, by Thomas Mathews (3 vols., Dublin, 1907), an ill-arranged and uncritical work, has little historical value, but contains a mass of traditional and legendary lore, and a number of translations of ancient poems, and genealogical tables of doubtful authority.
The O'Neills, always opposed to the English, had forfeited every baronial right; but in 1552 Hugh O'Neill of Clandeboye promised allegiance to the reigning monarch, and obtained the castle of Carrickfergus, the town and fortress of Belfast, and all the surrounding lands.
De Courci, however, soon obtained his liberty, probably by giving hostages as security for a promise of submission which he failed to carry out, seeking an asylum instead with the O'Neills of Tyrone.
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, 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 l 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 neighbours, and of their own efforts to make good their claims to the overlordship of northern Connaught.
In the 16th century, when the English began to make determined 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 enemies the O'Neills, at other times joining with the latter against the English authorities.
Hugh Dubh had been chief of the O'Donnells during one of the bitterest and most protracted of the feuds between his clan and the O'Neills, which in 1491 led to a war lasting more than ten years.
On his return from Rome in broken health after two years' absence, his son Manus, who had proved himself a capable leader in defending his country against the O'Neills, retained the chief authority.
A family quarrel ensued, and when Hugh Dubh appealed for aid against his son to the Maguires, Manus made an alliance with the O'Neills, by whose assistance he established his hold over Tyrconnel.
Although this was one of the bloodiest fights that ever took place between the O'Neills and the O'Donnells, it did not bring the war to an end; and in 1531 O'Donnell applied to the English government for protection, giving assurances of allegiance to Henry VIII.
Conn O'Neill was a relative of Gerald Fitzgerald, and this event accordingly led to the formation of the Geraldine League, a federation which combined the O'Neills, the O'Donnells, the O'Briens of Thomond, and other powerful clans; the primary object of which was to restore Gerald to the earldom of Kildare, but which afterwards aimed at the complete overthrow of English rule in Ireland.
His first wife, Joan O'Reilly, was the mother of Calvagh, and two daughters, both of whom married O'Neills; the younger, Margaret, was wife of the famous rebel Shane O'Neill.
Calvagh, acting apparently on the advice of his father, who was his prisoner and who remembered the successful night attack on Conn O'Neill at Knockavoe in 1522, surprised the O'Neills in their camp at night and routed them with the loss of all their spoils.
Niall Garve made terms with the English government, to whom he rendered valuable service both against the O'Neills and against his cousin.
These family connexions with the Hebridean Scots and with the O'Neills made the lord deputy, Sir John Perrot, afraid of a powerful combination against the English government, and induced him to establish garrisons in Tyrconnel and to demand hostages from Hugh MacManus O'Donnell, which the latter refused to hand over.