Domnall Midi (‘of Meath’) (d. 763), son of Murchad and king of Tara, belonged to the Clann Cholmáin dynasty of Uí Néill. Domnall's reign saw further consolidation of his dynasty's position in the midlands, and the forging of close links between the Southern Uí Néill (which by this time formed a distinct dynastic federation) and the Columban familia. His father Murchad Midi (qv) (d. 715), son of Diarmait son of Airmedach, is in the regnal lists as king of Uisnech. His mother, according to genealogical tradition, was Ailphin, daughter of Comgall king of Delbna; his only documented wife, Ailbéne daughter of Ailill king of Ard Cianachta, was the mother of Donnchad Midi (qv), his most prominent son. The mother(s) of his other sons are not recorded, but these included Murchad (or Muiredach, slain 765), Fiachu, Indrechtach, Fínshnechtae, and Diarmait Odar.
Domnall Midi may well have succeeded his father directly as ruler of Clann Cholmáin, but can hardly have been effective till after his father's slayer, Clann Chernaig dynast Conall Grant, was dispatched in 718. Reckoning from that date, Domnall reached the forty-sixth year of his kingship, which accords with the length of reign assigned to him in the king-lists. It is possible that he was helped to power in the first instance by the then king of Tara, Fergal (qv) son of Máel-dúin.
Domnall's early reign was inauspicious, although he seems to have supported the Southern Uí Néill cleric, Cilléne Droichtech, for the abbacy of Iona in 726. The first clear indication of his military prowess came in 733, when he repulsed the Munster overking Cathal (qv) son of Finguine from the ceremonial site of Tailtiu (Teltown, Co. Meath). In 740 Domnall took clerical orders; the ecclesiastical centre he entered is not named, but it seems likely that it was the Columban foundation of Durrow. Perhaps he combined some ecclesiastical role with his kingship; in any event, he remained politically active. Three years later, he defeated and slew the reigning king of Tara, Áed Allán (qv), along with his Cruthin allies, in an important battle at Seredmag (near Kells). Succeeding to the kingship of Tara, Domnall held that dignity for twenty years.
He resumed his clerical role in 744, and his reign as overking on the whole was peaceful if not necessarily prosperous. It seems that his ecclesiastical connections influenced his politics: in 748 the adoption throughout Leth Cuinn (the northern half of Ireland) of Lex Uí Shuanaich, an ecclesiastical law emanating from Rahan, quite possibly had his support. There are stronger grounds for considering (despite the death of his protégé Cilléne Droichtech at Iona and the succession of Sléibíne (qv), a Northern Uí Néill candidate) that he was behind the promulgation of the Law of Colum Cille (qv) in 753. Such levying of ecclesiastical dues often coincided with natural disasters or social disturbance, and so may point to a time of difficulty in his reign. Parallel to this, his close contacts with the church doubtless facilitated the documentation of dynastic affairs; certainly, the Uí Néill record comes into sharper focus from this period onwards, even if that did not necessarily involve a coordinated revision of the annals as has been claimed.
It may be valid to explain the relatively low level of military activity on Domnall's part in terms of a temporary satiation of Uí Néill power. There was some conflict with the Cruthin rulers of Airgialla, and Domnall's son Fiachu was slain by two dynasts of Fir Rois in north Co. Louth. It is probably significant that, unlike so many Uí Néill overkings, Domnall Midi never attacked the Uí Dúnlainge of northern Leinster. Achievement on his part of a modus vivendi with the latter dynasty seems all the more likely in view of his having recruited Leinster support in 756 for a campaign against the Northern Uí Néill king, Niall Frossach (qv).
Domnall died, appropriately enough, at Durrow on 20 November 763. His immediate successor in the Uisnech kingship is named in the regnal list as Niall son of Diarmait son of Airmedach; but as Diarmait had died back in 689, the dynast in question was in all probability a son of Niall and so a first cousin of Domnall. This cousin seemingly enjoyed a brief reign before being slain by Domnall's son Murchad (or Muiredach), the latter in turn being slain two years later by his own brother, Donnchad Midi, who regained the kingship of Tara for his lineage.