Áed Dub (‘black [haired]’) (d. 588), son of Suibne Araide and overking of Ulaid, belonged to the Dál nAraide dynasty of the Ulster Cruthin. He emerged as king of Dál nAraide after the battle of Móin Dairi Lothair (563), in which the Uí Néill severely defeated the Cruthin. Apparently, in 565 Áed killed the Uí Néill king of Tara, Diarmait (qv) son of Cerball. On that account he earned the wrath of later Uí Néill commentators, including Adomnán (qv) (d. 704), abbot of Iona, who presents the Dál nAraide king as an apostate priest (‘Vita Columbae’, i, §36), for whom Colum Cille (qv) foresaw an unseemly end, because ‘Áed the Black, verily a man of blood . . . had slain Diarmait the son of Cerball, who had been ordained by God's authority as ruler of all Ireland’. The point of the prophecy was perhaps to stress how wrong it was for Áed, as one in holy orders, to have taken arms against a (rightful) king; thus any suspicion that Colum Cille had taken an active part in the battle of Cúl Dreimne would surely be dispelled. By the Middle Irish period, an elaborated version of Áed's killing of Diarmait (as reflected in Clonmacnoise-centred annals) located the event at Ráith Becc, a Dál nAraide fortress in Mag Line (south Co. Antrim). Áed Dub features prominently in the legendary death-tale of Diarmait, wounding him with a spear as he flees a burning house. The Uí Néill version of events, as it developed, seems to imply that Áed acted treacherously towards his overlord: having received Diarmait as a guest (when he came to Mag Line seeking the hospitality owed by under-kings to their suzerains), he then murdered him. The reality may have been rather different.
Áed's dynasty was still powerful in the sixth (and early seventh) century, at times asserting its lordship as far south as the Boyne, and apparently contesting the kingship of Tara with the Uí Néill. If Áed did in fact kill Diarmait, it is more likely that this happened in the northern Boyne valley, where the ambitions of their respective dynasties overlapped. Such an action on his part suggests that he was a challenger for the kingship of Tara, and it is possible that he features in the Old Irish regnal poem ‘Baile Chuinn’. It seems, however, that he did not make good any claims to Tara; in fact, the regnal lists imply that he attained the overkingship of Ulaid only after the death of his Dál Fiatach rival Báetán (qv) son of Cairell, which is dated to 581. Áed was killed in 588 by Fiachnae Lurgan (qv), son of Báetán, another member of Dál nAraide. The account of his death relayed by Adomnán – claiming that he was speared aboard a ship, toppled from the prow, and drowned – seems to echo a version of ‘threefold death’, in which the victim was ritually wounded and fell from wood into water. Áed's genealogy has not survived, so that neither his antecedents nor his descendants are known. The kingship of Dál nAraide passed to his slayer, Fiachnae Lurgan.