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. The rise of the Uí Néill dynasties and their conquests in Ulster and Leinster are not reliably recorded and have been the subject of considerable study and attempts to reconstruct them. 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.

Historicity and dates

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.