Domnall mac Muirchertaig (died c

Circa

Circa , usually abbreviated c. or ca. , means "approximately" in the English language, usually referring to a date...

. 566), called Domnall Ilchelgach (Domnall of the Many Deceits) and Domnall mac Maic Ercae, was said to be a High King of Ireland

High King of Ireland

The High Kings of Ireland were sometimes historical and sometimes legendary figures who had, or who are claimed to have had, lordship over the whole of Ireland. Medieval and early modern Irish literature portrays an almost unbroken sequence of High Kings, ruling from Tara over a hierarchy of...

.

Domnall was probably a son of Muirchertach mac Muiredaig

Muirchertach mac Muiredaig

Muirchertach mac Muiredaig , called Mac Ercae, Muirchertach Macc Ercae and Muirchertach mac Ercae, was said to be High King of Ireland. The Irish annals contain little reliable information on his life, and the surviving record shows signs of retrospective modification...

, and belonged to that part the northern branch of the Uí Néill

Uí Néill

The Uí Néill are Irish and Scottish dynasties who claim descent from Niall Noigiallach , an historical King of Tara who died about 405....

—the kindred name is probably anachronistic in his time and dates from perhaps a generation later—which would later be known as the Cenél nEógain

Cenél nEógain

Cenél nEóġain is the name of the "kindred" or descendants of Eógan mac Néill , son of Niall Noígiallach who founded the kingdom of Tír Eoghain in the 5th century...

. Together with his brother Forggus

Forggus mac Muirchertaig

Forggus mac Muirchertaig , also called Forrgus mac Maic Ercae, is included in most lists of High Kings of Ireland.Father Muirchertach mac Muiredaig, also called Mac Ercae, brother Domnall Ilchelgach with whom he is said to have ruled jointly...

, and perhaps also their kinsman Ainmuire mac Sétnai

Ainmuire mac Sétnai

Ainmuire mac Sétnai or Ainmire or Ainmere was a High King of Ireland from the Cenél Conaill branch of the Uí Néill. He was the great grandson of Conall Gulban , founder of this branch. He ruled from 566-569...

, he is said to have been High King following the death of Diarmait mac Cerbaill

Diarmait mac Cerbaill

Diarmait mac Cerbaill was King of Tara or High King of Ireland. According to traditions, he was the last High King to follow the pagan rituals of inauguration, the ban-feis or marriage to goddess of the land....

, whose enemy they had been. The beginning of their reign is conventionally dated to c. 565, based on the testimony of the Annals of Ulster

Annals of Ulster

The Annals of Ulster are annals of medieval Ireland. The entries span the years between AD 431 to AD 1540. The entries up to AD 1489 were compiled in the late 15th century by the scribe Ruaidhrí Ó Luinín, under his patron Cathal Óg Mac Maghnusa on the island of Belle Isle on Lough Erne in the...

, but recent studies have suggested that this is several years too late and that the dates in the Annals of Tigernach

Annals of Tigernach

The Annals of Tigernach is a chronicle probably originating in Clonmacnoise, Ireland. The language is a mixture of Latin and Old and Middle Irish....

are more reliable in this period.

Domnall, Forggus and Ainmuire, perhaps with the aid of Áed mac Echach

Áed mac Echach

Áed mac Echach Tirmcharna was a King of Connacht from the Uí Briúin branch of the Connachta. He was the son of Echu Tirmcharna mac Fergusso . He came to the throne in the year 557 and ruled till 575....

, King of Connacht defeated Diarmait mac Cerbaill at the battle of Cúl Dreimne in the early 560s, but Diarmait retained his hold on power. His authority may have been strengthened by the decisive defeat which Domnall, Forggus and their allies inflicted on the cruithne of Ulster

Ulster

Ulster is one of the four provinces of Ireland, located in the north of the island. In ancient Ireland, it was one of the fifths ruled by a "king of over-kings" . Following the Norman invasion of Ireland, the ancient kingdoms were shired into a number of counties for administrative and judicial...

 at the battle of Móin Daire Lothair in the year following Cúl Dreimne. Domnall and Forggus are thought to have been recognised as Diarmait's successors after Cúl Dreimne. Their joint reign was short, a battle in the lands of the River Liffey

River Liffey

The Liffey is a river in Ireland, which flows through the centre of Dublin. Its major tributaries include the River Dodder, the River Poddle and the River Camac. The river supplies much of Dublin's water, and a range of recreational opportunities.-Name:The river was previously named An Ruirthech,...

 in Leinster

Leinster

Leinster is one of the Provinces of Ireland situated in the east of Ireland. It comprises the ancient Kingdoms of Mide, Osraige and Leinster. Following the Norman invasion of Ireland, the historic fifths of Leinster and Mide gradually merged, mainly due to the impact of the Pale, which straddled...

 being recorded shortly before Domnall's death in about 566.

Domnall's sons Eochaid

Eochaid mac Domnaill

Eochaid mac Domnaill , also Eochaid Find , was an Irish king who is included in some lists as a High King of Ireland. He was the son of Domnall Ilchelgach and grandson of Muirchertach mac Muiredaig , also considered high kings. He was a member of the Cenél nEógain branch of the northern Uí Néill...

 and Áed

Áed Uaridnach

Áed Uaridnach was an Irish king who was High King of Ireland. He is sometimes also known as Áed Allán, a name most commonly used for the 8th century king of the same name, this Áed's great-great-grandson....

were reckoned High Kings and the great majority of Cenél nEógain kings counted as High Kings of Ireland were his descendants.