Donnchad Midi (‘of Meath’) (d. 797), son of Domnall Midi and king of Tara, belonged to the Clann Cholmáin dynasty of the Southern Uí Néill. Arguably the most powerful Irish king of his day, Donnchad suppressed resistance within his own province of Meath, acted as kingmaker in Leinster, subdued Munster, and overawed the north. His father was Domnall Midi (qv), king of Tara, and his mother Ailbéne, daughter of Ailill, king of Ard Cianachta. Donnchad had at least five brothers or half-brothers, including Murchad (or Muiredach, slain 765), Fiachu, Indrechtach, Fínshnechtae, and Diarmait Odar.
Donnchad first came to prominence in the years immediately following his father's death at the Columban foundation of Durrow (763). A cousin, the son of Niall son of Diarmait, who laid claim to the Southern Uí Néill kingship of Uisnech, was slain by Donnchad's brother Murchad. Displaying a ruthlessness that would later characterise succession to the Uisnech kingship, Donnchad overthrew his brother in the battle of Carn (765) and took his place. It seems that Donnchad subsequently had his own ally, Folloman son of Cú Chongalt, slain. He may also have dispatched his brother; although a Murchad son of Domnall was still alive in 799, it is not certain that this was the same individual.
Meanwhile, Donnchad apparently pursued a policy of securing marriage alliances with the ruling dynasties of the north-east. He married Fuirsech, daughter of Congal king of Dál nAraide, mother of his son Conchobar (qv). Another of Donnchad's wives, Bébail, daughter of Cathal king of Ulster, was the mother of his sons Máel-ruanaid and Óengus. He apparently had five other sons, whose mothers are not recorded: Domnall (slain 799), Aillill and Diarmait (both slain 803), Folloman (slain 830), and perhaps also Ruaidrí (d. 838), vice-abbot of Clonard and Clonmacnoise. He also had at least three daughters: Eithne (qv), the wife of Bran Ardchenn (qv) the nominal overking of Leinster; Euginis, who died in 803 as ‘queen of the king of Tara’ – seemingly, wife of Áed Oirdnide (qv) of Cenél nÉogain; and Gormlaith (d. 861), who married the latter's son Niall Caille (qv) and was the mother of Áed Finnliath (qv).
As king of Uisnech, Donnchad led an expedition south-eastwards in 770. Sustaining a minor defeat from the Leinster king Cellach (qv) son of Dúnchad (qv) near Castledermot, he camped at Dún Ailinne (Knockaulin, Co. Kildare) and ravaged the surrounding countryside, asserting Uí Néill suzerainty over Leinster. The same year, he hosted to the north but with no clear result. In 772 he again led a hosting northwards, this time to Cnoc Báine (Co. Tyrone). It may have been at this stage that the nominal king of Tara, Niall Frossach (qv), abdicated; such an inference can certainly be taken from the Tara regnal list in the Book of Leinster, which assigns Donnchad a reign of twenty-five years (cf. the Rawlinson B. 502 list, which accords him twenty-seven years). In any case, the early 770s saw Donnchad consolidating his power as overking of the Uí Néill; the disturbance at the fair of Tailtiu in 774 was probably a result of the ensuing political unrest. The skirmish at the ecclesiastical centre of Clonard the following year might be viewed in a similar light.
Now ensconced as king of Tara, in 775 Donnchad invaded Munster, causing much devastation. His control of a ‘midland corridor’ is suggested by the fact that he returned a year later, backed up by forces from the Columban settlement of Durrow. Although he sustained heavy losses on this occasion, including several of his kinsmen, he was nevertheless victorious. Opposition had by this time surfaced within the province of Meath, in particular from the Síl nÁedo Sláine dynasty of Brega. In 778 he secured the support of the Leinstermen to defeat and slay Congalach, king of northern Brega, at Forcalad. Nor was that an end to the matter; eight years later, he was forced to take the field at Liath Finn against another lineage of Síl nÁedo Sláine. Meanwhile, in 780 he reasserted his authority over Leinster, defeating the king, Ruaidrí son of Fáelán, at Kilcock on the Kildare–Meath border.
Ruaidrí's death five years later provided an opportunity for Donnchad to act as kingmaker in Leinster; he lent support to the cause of his son-in-law, Bran Ardchenn, husband of his daughter Eithne. Donnchad, in turn, had Bran's backing for an expedition against Munster in 794. Nor did he waver in his efforts to retain an influence over the north. Carefully monitoring the emergence of the powerful Ulster king Fiachnae (qv) son of Áed Rón (qv), in 784 he secured a rígdál (royal meeting) at Inis na Ríg, off the coast of Meath. It seems clear that the object was to delimit spheres of influence; the location of the meeting in Donnchad's realm, however, and the reluctance of the Ulster king to leave his ship, suggest that the king of Tara held the upper hand. There are indications that by this stage Donnchad was intervening with increasing success in the territories of Airthir and Uí Echdach, within the present counties of Armagh and Down. He also overawed the leading Northern Uí Néill king, Domnall son of Áed Muinderg.
Donnchad was prominently involved in religious affairs, in most cases with a clear political agenda. His attack on Clonard in 775 preceded the elevation to the abbacy, against conflicting claims, of Dub-dá-Bairenn grandson of Dubán (d. 805) – the first head of Clonard to be styled princeps in the Annals of Ulster, a title that many scholars interpret as ‘royal abbot’. In 780 he facilitated a provincial synod at Tara under Dublittir (qv) of Finglas, although it is claimed that he dishonoured the Bachall Ísu – an important Patrician relic – at Ráith Airthir in 789.
Although opposition to Donnchad's designs was long muted due to internal fighting among the Northern Uí Néill dynasties, Áed Oirdnide eventually emerged to pose a serious threat. For a time it appeared that Donnchad was able to restrain his son-in-law; in 791 he defeated his challenge at Tailtiu before turning to reassert his authority over Munster. In 797, however, Donnchad met his end, the same year his brother Indrechtach died. He may well have been slain by Áed in the battle of Drumree (Co. Meath), as the regnal list states. Certainly, his brothers Diarmait Odar and Fínshnechtae fell in that battle (AU).
Following Donnchad's death, his sons took to fighting among themselves, as a result of which Domnall was slain in 799 by agents unknown. In 802 Áed Oirdnide succeeded in dividing Meath between Conchobar, Diarmait, and Ailill, before Conchobar (d. 833) made himself sole ruler by slaying his brothers at the battle of Ruba Conaill. Of the remaining sons of Donnchad, the death of Óengus is unrecorded, Folloman was slain in 830, and it was from Máel-ruanaid (d. 843) – the father in turn of Máel-Sechnaill (qv) – that the later kings of the Clann Cholmáin dynasty descended.