[[Ard-Rí na hÉireann]] ba ea '''DomnallDomhnall mac MuirchertaigMuircheartaigh''' (died ''[[circa|cSean-Ghaeilge]] '''Domnall mac Muirchertaig''') (bás c. 566), calledar 'a glaodh Domhnall Ilchealgach (''Domnall Ilchelgach''') (Domnallagus ofDomhnall themac Many Deceits)Mhic andEarca '(''Domnall mac Maic Ercae''', was said to be a [[High King of Ireland]]).
Domnall''Domhnall was a son of [[Muirchertach mac Muiredaig|Muircheartach mac Muireadaigh]], and belonged to that part the northern branch of the [[Uí Néill]]—thekindred name is probably [[anachronistic]] in his time and dates from perhaps a generation later—which would later be known as the [[CenélCineál nEógainEoghain]]. Together with his brother ''[[Forggus mac Muirchertaig|ForggusForghas]]'', and perhaps also their kinsman [[Ainmuire mac Sétnai|Ainmhire mac Seanna]], he is said to have been High King following the death of their enemy, [[DiarmaitDiarmaid mac CerbaillCearbhaill]],. whose enemy they had been. The beginning of their reign is conventionally dated to ''c''. 565, based on the testimony of the ''[[AnnalsAnnála of UlsterUladh]]'', but recent studies have suggested that this is several years too late and that the dates in the ''[[AnnalsAnnála of TigernachTiarnaigh]]'' are more reliable in this period.
Domnall''Domhnall, Forggus''Forghas'' and AinmuireAinmhire, perhaps with the aid of [[Áed mac Echach|Aodh mac Eachach]], [[Kingrí ofna ConnachtgConnacht]] defeated DiarmaitDiarmaid mac CerbaillCearbhaill at the [[BattleCath of CúlChúl Dreimhne]] in the early 560s, but DiarmaitDiarmaid retained his hold on power. His authority may have been strengthened by the decisive defeat which DomnallDomhnall, ForggusForghas and their allies inflicted on the [[cruithne (people)|cruithneCruithne]] ofag [[Ulster]]Cath at the [[battle of MóinMhóin Daire Lothair]] in the year following Cúl Dreimneyear. DomnallDomhnall and ForggusForghas are thought to have been recognised as Diarmait'sDiarmada successors after Cúl Dreimne. Their joint reign was short,. a A battle in the lands of the [[RiverAn LiffeyLife]] in [[Leinster]] beingwas recorded shortly before Domnall's death in about 566.
Domnall''Domhnall's sons [[Eochaid mac Domnaill|EochaidEochaidh]] and [[Áed Uaridnach|Aodh Fuariodhnach]] were reckoned High Kings and the great majority of CenélCineál nEógain kings counted asEoghain High Kings of Ireland were his descendants.
