The Uí Briúin were a royal dynasty of Connacht. Their eponymous apical ancestor was Brión, son of Eochaid Mugmedon and Mongfind, and an elder half brother of Niall of the Nine Hostages. They formed part of the Connachta, along with the Uí Fiachrach and Uí Ailello, putative descendants of Eochaid Mugmedon's sons Fiachra and Ailill. The Uí Ailello were later replaced as the third of the Three Connachta, by genealogical sleight of hand, by the Uí Maine.
Connacht was ruled in early times by the Uí Fiachrach, the Uí Briúin only becoming the dominant force in Connacht in the 7th and 8th centuries.
The Uí Briúin divided into multiple septs, the three major ones being:
The Uí Briúin kings of Connacht were drawn exclusively from these three branches.
According to Tírechán, Saint Patrick visited the "halls of the sons of Brión" at Duma Selchae (located by John O'Donovan in Mag nAí and alternatively by Roderic O'Flaherty near Loch Cime), but does not give their names. An equivalent passage in the Vita Tripartita, possibly of 9th-century origin, names six sons. "A series of later sources dating from the eleventh century onward, meanwhile, enumerates Brion's progeny as no less than twenty-four. No doubt the increasing power of the Uí Briúin was responsible for this dramatic swelling of the ranks, as tribes and dynasties newly coming under Uí Briúin sway were furnished with ancestries that would link them genealogically to their overlords. Into this category fall the Uí Briúin Umaill and likely also the Uí Briúin Ratha and Uí Briúin Sinna."
While Francis Byrne and John O'Donovan believed the dynasty originated in Mag nAí, Roderic O'Flaherty and John Colgan related traditions of Saints Patrickand Felartus visiting the sons of Brión in Maigh Seóla. This confusion surrounding the location of Mag Selce as mentioned in the Tripartite caused Nicholls to suggest that the geographical origin of the Uí Briúin was moved for political reasons to near Cruachan by the time of Tírechán. MacCotter also points out that when the Uí Briúin were purportedly beginning their ascent, given the distributions of surrounding population groups, "the area originally available to Uí Briúin [in Mag nAí] cannot have consisted of more than the area of a few civil parishes", which may lend support to Nicholls' theory.
A story in the Silva Gadelicanotes that during the legendary war between Brión and Fiachra, Fiachra's encampment was situated in Aidhne and Brión's lay in Damh-Chluain, which is stated to be in Uí Briúin Seóla and not far from Knockma Hill, west of Tuam. Although this is a legend, it may be an indication of the Uí Briúin's original homeland, as is Aidhne for the Uí Fiachrach. In addition, Hubert Knox, citing the Conmaicne's distribution and early status as subjects of the Uí Briúin, posited that the Uí Briúin originated in the barony of Clare in County Galway as the leading lineage of that people. Intriguingly, the Book of Ballymote calls Cellach mac Rogallaig "King of Conmaicne", a title also commonly taken by members of the Uí Briúin Bréifne branch in later centuries. The Maigh Seóla origin scenario is more consistent with the fact that early Uí Briúin kings (e.g. Cenn Fáelad mac Colgan and Cellach mac Rogallaig) had their residence on Loch Cime, as well as Áed mac Echach's donation of Annaghdown in the 6th century, which Byrne thought unlikely given Annaghdown's distance from Mag nAí. With the inclusion of Máenach mac Báethíne, ancestors of all three major branches of the dynasty are mentioned in the annals as residing or fighting in the Maigh Seóla region in the 7th century. The district to the east of Lough Corrib and the River Corrib is referred to as "Magh Ua mBriuin" at least as late as 1149. This likely denotes the domain of the "king of Uí Briúin", a title borne primarily by men of the Uí Briúin Seóla. As Knox points out, these kings were distinguished at an early date from the Síol Muireadaigh of central Roscommon in the Book of Rights, suggesting that the lands of the Uí Briúin Seóla were the original "Hy Briuin".
Uí Fhiachrach Aidhne was a kingdom located in what is now the south of County Galway.
The Connachta are a group of medieval Irish dynasties who claimed descent from the legendary High King Conn Cétchathach. The modern western province of Connacht takes its name from them, although the territories of the Connachta also included at various times parts of southern and western Ulster and northern Leinster. Their traditional capital was Cruachan.
Maigh Seóla, also known as Hy Briuin Seola, was the territory that included land along the east shore of Lough Corrib in County Galway, Ireland. It was bounded to the east by the Uí Maine vassal kingdom of Soghain and extended roughly from what is now Clarinbridge in the south to Knockmaa Hill in the north. Its rulers belonged to the Uí Briúin Seóla and are sometimes found in the annals under the title "King of Uí Briúin" and "King of South Connacht". The earliest identifiable kings belonged to the line that became the Clann Cosgraigh. However in later times the line which would become the Muintir Murchada, under the O'Flaherty chiefs, monopolized the kingship.
Brión, son of Eochaid Mugmedón, was a legendary and possibly historical Irish king, fl. 4th/5th century.
O'Flaherty, is an Irish Gaelic clan based most prominently in what is today County Galway. The clan name originated in the 10th century as a derivative of its founder Flaithbheartach mac Eimhin. They descend in the paternal line from the Connachta's Uí Briúin Seóla. They were originally kings of Maigh Seóla and Muintir Murchada and as members of the Uí Briúin were kinsmen of the Ó Conchubhair and Mac Diarmada amongst others. After their king Cathal mac Tigernán lost out to Áed in Gai Bernaig in the 11th century, the family were pushed further west to Iar Connacht, a territory associated with Connemara today. They continued to rule this land until the 16th century.
Nath Í, also known as Dathí, son of Fiachrae, son of Eochaid Mugmedon, was a semi-historical Irish king of the 5th century, the father of the likely-historical king Ailill Molt and the ancestor of the Uí Fiachrach dynasties of early medieval Connacht. His mother was Béḃinn. According to legend, he was a High King of Ireland, and died after being struck by lightning while on an expedition to the Alps.
Cathal mac Conchobair was King of Connacht.
Rogallach mac Uatach was a king of Connacht from the Uí Briúin branch of the Connachta. He was the son of Uatu mac Áedo, a previous king. He married Muireann, the great-great-great-granddaughter of Túathal Máelgarb, High King of Ireland. He acquired the throne of Connacht after defeating the previous king Colmán mac Cobthaig of the Ui Fiachrach Aidhne, who was slain at the Battle of Cennbag in 622. Professor Francis Byrne believes he is the first reasonable representative of this branch to be said to have held the throne of Connacht
Dauí Tenga Uma was a King of Connacht from the Uí Briúin branch of the Connachta.
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 until 575.
Loingsech mac Colmáin was a king of Connacht from the Ui Fiachrach branch of the Connachta. He was of the Ui Fiachrach Aidhne sept this branch and was the son of Colmán mac Cobthaig.
Cenn Fáelad mac Colgan was a King of Connacht from the Uí Briúin branch of the Connachta. He was of the branch which developed into the Uí Briúin Seóla, who were centred on Tuam in modern County Galway. He is the first member of this branch mentioned in the annals.
Muiredach Muillethan mac Fergusso was a King of Connacht from the Uí Briúin Aí branch of the Uí Briúin. He was the grandson of Rogallach mac Uatach, a previous king. His sobriquet Muillethan means "broad-crowned".
Forggus mac Cellaig was a King of Connacht from the Uí Briúin branch of the Connachta. He was the son of Cellach mac Rogallaig, a previous king and brother of Domnall mac Cellaig. The sept of Uí Briúin Ai he belonged to was the Síl Cellaig of Loch Cime named for his father. He reigned from 742 to 756.
Ruaidrí Ua Conchobair, called Ruaidrí na Saide Buide was King of Connacht, perhaps twice.
Diarmait mac Tommaltaig was a king of Connacht from the Uí Briúin branch of the Connachta. He was the great-grandson of Indrechtach mac Muiredaig Muillethan, a previous king. The death of his father Tommaltach mac Murgail is recorded in the annals where he is called king of Mag nAi. He succeeded his brother Muirgius mac Tommaltaig. He was of the Síl Muiredaig sept of the Uí Briúin. He ruled from 815 to 833.
Urchadh mac Murchadh was King of Maigh Seóla.
Maelan mac Cathmogha was King of Maigh Seóla.
Donn mac Cumasgach was a king of Maigh Seóla who died in 752.
The Uí Fiachrach were a royal dynasty who originated in, and whose descendants later ruled, the coicead or fifth of Connacht at different times from the mid-first millennium onwards. They claimed descent from Fiachrae, an older half-brother of Niall Noigiallach or Niall of the Nine Hostages. Fiachrae and his two full brothers, Brion and Ailill, were the collective ancestors of the Connachta dynasty that eventually became the new name of the province. Their mother was Mongfind.