Niall of the nine hostages

Niall Noígíallach (Irish pronunciation: [ˈniːəl noɪˈɣiːələx], Old Irish "having nine hostages"), or in English, Niall of the Nine Hostages, was a prehistoric Irish king, the ancestor of the Uí Néill family that dominated Ireland from the 6th to the 10th century. Irish annalistic and chronicle sources place his reign in the late 4th and early 5th centuries, although modern scholars, through critical study of the annals, date him about half a century later. He is presumed to have been a real person, but most of the information about him that has come down to us is legendary.

Niall is presumed, on the basis of the importance of his sons and grandsons, to have been a historical person, but the early Irish annals say little about him. The Annals of Inisfallen date his death before 382, and the Chronicon Scotorum to 411. The later Annals of the Four Masters dates his reign to 379-405, and the chronology of Geoffrey Keating's Foras Feasa ar Éirinn to 368–395.

However, the early annals record the activities of his sons between 429 and 516, an implausibly long time-span for a single generation, leading scholars like Kathleen Hughes and Francis J. Byrne to conclude that the events of the later half of the 5th century have been extended backwards to accommodate as early a date as possible for the arrival of Saint Patrick, with the effect of pushing Niall back up to half a century. Hughes says "Niall himself must have died not before the middle of the fifth century". Byrne, following James Carney, is a little more precise, dating his death to c. 452.

T. F. O'Rahilly argues that Niall and his sons were responsible for the breakup of the ancient kingdom of Ulster and the creation of the kingdoms of Tír Chonaill and Tír Eógan, and the satellite kingdom of the Airgíalla. O'Rahilly and Byrne argue that the literary sources, though late and garbled, preserve genuine traditions that Niall led raids on Britain, and perhaps died on one.

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