Áed mac Néill (; died 819), commonly called Áed Oirdnide ("the anointed"), was King of Ailech. A member of the Cenél nEógain dynasty of the northern Uí Néill, he was the son of Niall Frossach. Like his father, Áed was reckoned High King of Ireland. He was King of Ailech from 788 onwards and High King of Ireland from 797. King of Ailech The conflict between Cenél nEógain and Cenél Conaill for the leading role in the north appears to have turned on control over the lands of the minor Cenél nEndai branch of the Uí Néill which lay around Raphoe. Communications between the northern and southern branches of Cenél Conaill, respectively based on the north-west coast of Donergal and in the south around Donegal town, ran through these. While Cenél nEndai were clients or allies of Cenél Conaill, as they had been before Áed Allán defeated Flaithbertach mac Loingsig in the 730s, Cenél Conaill had the upper hand, and provided kings of Tara and kings of the North. By the death of Niall Frossach, if not earlier, Cenél nEndai were again under the sway of Cenél Conaill. The region was still disputed in 787 when Máel Dúin defeated Domnall and appears to have gained some recognition as king of the North as he is so styled at his death the following year. Áed succeeded Máel Dúin as king of Ailech, but was challenged by Domnall whom he defeated at the battle of Clóitech (modern Clady, County Tyrone) in 789. This appears to have been the final attempt by kings of Cenél Conaill to regain control of the lands around Raphoe which had been seized by Cenél nEógain. The annals record a battle in 791 at Tailtiu, site of a major Uí Néill oenach, the oenach Tailten. The summoning of this gathering was one of the prerogatives of the High King at which he would demonstrate his power and standing. Whether Áed brought an army south to disturb the oenach, or whether the conflict was provoked by Donnchad, is unknown. The outcome was that Áed fled from Tailtiu and was pursued perhaps as far as Slane. Several of Áed's allies are said to have been killed, including the kings of two branches of Uí Chremthainn, an Airgíalla dynasty whose lands lay around Clogher and Clones. It is on this occasion that the Chronicle of Ireland calls Áed Áed Ingor, Áed