Áed (d. 598), son of Ainmere and overking of Uí Néill, belonged to Cenél Conaill, one of the leading dynasties of Uí Néill. His father Ainmere (qv) (d. 569), a first cousin of Colum Cille (qv), was included in Middle Irish lists of the kings of Tara, and was certainly a powerful political figure in the 560s. His mother, according to the ‘Banshenchas’ (lore of women), was Brigit daughter of Cobthach, an Uí Chennselaig dynast. It is claimed that from another marriage (to Maine son of Fergus of Dál Messin Corb), she had sons, Étchén and Áedán, both bishops, the latter associated with Glendalough. Áed in turn married Lann daughter of Áed Guaire, king of Airgialla; she was the mother of his sons Máel-Cobo (slain 615) and Domnall (qv) (d. 642). He had at least three other sons, Conall Cú (d. 604), Crunnmáel, and Cummascach.
Although Middle Irish regnal lists accord Áed a reign of twenty-eight years as king of Tara, implying that he succeeded to that dignity c.570, there is little to indicate that he had achieved much prominence before that date, or indeed attained paramount kingship of Uí Néill till considerably later. There is no record, for instance, of his taking part in the important battle between Uí Néill dynasties at Cúl Dreimne (near Drumcliff, Co. Sligo; 561). From 570, however, he features increasingly in the record – not least because of the struggle with his Cenél nÉogain rivals. That year, he slew one of their leading dynasts, Fergus son of Néillíne, who had previously killed his father. Perhaps he gained control of Cenél Conaill about this time, which could explain the length of his reign in the regnal lists. Upholding the rights of his dynasty, he again defeated Cenél nÉogain at the battle of Druim Meic Erce (Drumahirk, Co. Tyrone) in 580/81. Meanwhile, it seems that Áed supported his cousin Báetán (qv) son of Ninnid, overking of Uí Néill 572–86. His victories over Cenél nÉogain notwithstanding, there is little to substantiate claims that Áed was protector of his cousin's kingship. In 586, however, Áed avenged Báetán's death by killing the instigator of his assassination, their kinsman and rival Colmán Bec (qv), at the battle of Belach Dathí (probably in the parish of Killucan, Co. Westmeath).
Soon afterwards, Áed attained overkingship of Uí Néill. According to ‘Baile in Scáil’ and Middle Irish regnal lists, he was king of Tara – but he is not so styled in the main hand of the Annals of Ulster, nor may he be confidently identified in the Old Irish regnal poem ‘Baile Chuinn’. A bitter enemy of the Laigin, whose kings continued to claim sway over parts of Mide, Áed invaded Leinster in 598. According to the story ‘Bóruma Laigen’ (‘cattle-tribute of the Leinstermen’) Áed sought vengeance when his son Cummascach was killed by Brandub (qv) son of Eochu, overking of Leinster. He persisted with his designs, although his half-brother Bishop Áedán tried to pacify the two enemies. In any case, a battle was fought at Dún Bolg (location uncertain), where Áed was defeated and slain. This victory of the Leinstermen is celebrated in the Latin Life (§§24, 26) of St Máedóc (qv) of Ferns.
Hagiography from the Uí Néill sphere of influence, however, portrays Áed in a more positive light. Certainly, he was the most powerful representative of Uí Néill dynastic interests at the time of the foundation of Durrow by Colum Cille, assuming that this took place towards the end of the sixth century. It is not inappropriate that he should be credited with commissioning the Old Irish hymn ‘Amra Choluim Cille’ in honour of his saintly cousin. According to Colum Cille's biographer Adomnán (qv) (‘Vita Columbae’, i, §§10–11, 49), he presided at the convention of Druim Cett (near Limavady, Co. Londonderry), noted in the annals at 575. Certain chronological considerations suggest a later date for Druim Cett; given the annalistic record of Áed's rise to power, it may be doubted that he had achieved sufficient political weight by 575 to preside at such a convention. Besides, the reported presence there of his son Domnall, who lived till 642, seems to support a date post 587. Later tradition alleges that Áed used the convention to threaten banishment on the poets of Ireland. In all probability, however, its purpose was to form an alliance between Áed and Áedán (qv) son of Gabrán, king of Dál Riata, against their mutual enemy, the overking of Ulster – either Báetán (qv) (d. 581) son of Cairell or Fiachnae Lurgan (qv) (d. 626), depending on whether the earlier or later date is accepted. It seems that an agreement was reached whereby the Irish-based forces and fleet of Dál Riata would be subject not to the overking of Ulaid but to the Uí Néill, while their Scottish territories would be independent. This would have shifted the balance of power in the north-east in favour of Áed. After Áed's death, his son Conall Cú was defeated by Cenél nÉogain, and died two years later. Máel-Cobo and Domnall held the kingship of Cenél Conaill in turn, the latter eventually succeeding to the kingship of Tara. Meanwhile, dynastic rivals including Áed Sláine (qv), Colmán Rímid (qv), and Áed Uaridnach (qv), claimed paramount kingship of the Uí Néill.