Origins
From the late eighth century until the Anglo-Norman invasion, the Uf Briuin were the most powerful dynasty in Connacht. Their eponym—Brion son of Eochu Mugmedon, king of Ireland, by Mongfhind, daughter of the Munster king Feradach son of Dare Cerbba— is depicted by the genealogies and saga literature as the elder brother of Fiachrach and Ailill, ancestors of the early Connacht dynasties of Uf Fiachrach and Uf Ailella. Their half-brother, the son of Eochu by the British slave girl Cairenn Casdub, was said to be Niall Nofgiallach ("of the Nine Hostages"), ancestor of the Uf Neill. It is uncertain whether the depiction of the eponyms as brothers reflects actual bonds of kinship or was simply a biological metaphor for political relationships between the dynasties concerned.
Dynasts alleged by the genealogists to have been members of the Uf Briuin appear in the annals by the early sixth century. The earliest references to Uf Briuin specifically as a dynasty, however, are mid-seventh century, occurring both within a series of annal entries and in Tfrechan’s life of Patrick. Tirechan relates that the saint traveled to Duma Selchae in Mag nAf, where the "halls of the sons of Brion" were located. Tirechan neither enumerates nor names these sons, but the equivalent passage in the Vita Tripartita, a possibly ninth-century life of Patrick, names six sons of Brion. 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 Uf Briuin was responsible for this dramatic swelling of the ranks, as tribes and dynasties newly coming under Uf Briuin sway were furnished with ancestries that would link them genealogically to their overlords. Into this category fall the Uf Briuin Umaill and likely also the Uf Briuin Ratha and Uf Briuin Sinna.
Uf Briuin Af
According to the later sources, Brion’s youngest son, Duf Galach, was the ancestor of the three most important branches of the dynasty: Uf Briuin Af, Uf Briuin Breifne, and Uf Briuin Seola. Of the three, by far the most powerful branch of the dynasty was Uf Briuin Af, based in Mag nAf in north-central County Roscommon. Throughout the seventh and first half of the eighth centuries, Uf Briuin Af struggled with Uf Fiachrach to control the kingship of Connacht. By the end of the eighth century, they had managed to squeeze out their Uf Fiachrach rivals to gain a near monopoly on the provincial kingship. At this point, the controlling branch of the Uf Briuin was a sept known as Sfl Muiredaig whose ruling family were to become the Ua Conchobair dynasty. Spreading out from their Mag nAf homeland, Sfl Muiredaig took direct control over most of modern County Roscommon and much of east Galway, in addition to their overlordship of the rest of the province.
From the late eighth century until the coming of the Anglo-Normans, Uf Briuin Af provided all but six kings of Connacht. They lost their grasp on the kingship once in the mid-tenth century as a consequence of intense rivalry from within Sfl Muiredaig, and five times in the eleventh century when they faced fierce opposition from Uf Briuin Breifne and Uf Briuin Seola within Connacht, and from the Uf Briain of Munster without. After the vicissitudes of the eleventh century, however, the Uf Briuin Af made a remarkable recovery in the twelfth, not only firmly recovering the kingship of Connacht but also gaining the kingship of Ireland in the personages of Tairrdelbach Ua Conchobair and his son Ruaidri.
Uf Briuin Breifne
On those occasions when Uf Briuin Af lost control of the Connacht kingship, it was predominantly dynasts from Uf Briuin Breifne, specifically the ruling family of Ua Ruairc, who seized the kingship. Having crossed east of the Shannon by the late eighth century into present day counties Leitrim and Cavan, Uf Briuin Breifne gradually expanded in a diagonal direction so that at the peak of their power in the late twelfth century they controlled a diagonal band of territory stretching from Leitrim and northeast Sligo down to Kells and Drogheda. Although under the suzerainty of the king of Connacht, most of this kingdom lay beyond the technical limits of the province, defined as west of the Shannon.
Uf Briuin Seola
Least powerful of the three main Uf Briuin dynasties, but by no means inconsequential, were Uf Briuin Seola. Also known as the kings of "Uf Briuin In Deisceirt" ("Uf Briuin of the south") and of "Iar-Chonnacht" ("west Connacht"), the Uf Briuin Seola were based in the area around Moyola, County Galway, east of Lough Corrib. Their two main divisions were the Clann Coscraig, whose ruling family were the Meic Aeda, and the Muinter Murchada, whose ruling family were the Uf Flaithbertaig. By the end of the eleventh century, the Ua Flaithbertaig family were dominant within the Uf Briuin Seola and indeed managed to very briefly take the provincial kingship in 1098 during the height of dynastic instability within Connacht. In the mid-thirteenth century, the Uf Flaithbertaig were deprived of their possessions east of the Corrib by the de Burgh family and moved west into present-day Connemara.
Common Uf Briuin Identity
Until the first half of the eleventh century, the various Uf Briuin dynasties seemed to actively maintain some sort of common Uf Briuin identity. Up until at least the 1030s, there existed a title "king of Uf Briuin" that was mostly bestowed upon the rulers of Uf Briuin Seola, functioning as subkings under the Ua Conchobair kings of Connacht. Likely due to the dissension of the eleventh century, however, the names of the constituent elements of the dynasty thereafter proclaimed themselves to be much more discrete entities. Uf Briuin Af became known exclusively as Sfl Muiredaig, while Uf Briuin Seola became known solely by the territorial designation of Iar-Chonnacht. Only Uf Briuin Breifne retained the "Uf Briuin" element of their name, so much so that by at least the beginning of the twelfth century, the term Uf Briuin denoted Uf Briuin Breifne alone.
