The popular image of Brian—the ruler who managed to unify the regional leaders of Ireland so as to free the land from a 'Danish' (Viking) occupation—originates from the powerful influence of a work of 12th century propaganda, Cogadh Gaedhil re Gallaibh (The War of the Irish with the Foreigners) in which Brian takes the leading role. This work is thought to have been commissioned by Brian's great-grandson,Muirchertach Ua Briain, as a means of justifying the Ua Briain claim to the High-Kingship, a title upon which the Uí Neill had had a near-monopoly.
The influence of this work, on both scholarly and popular authors, cannot be exaggerated. Until the 1970s most scholarly writing concerning the Vikings' activities in Ireland, as well as the career of Brian Boru, accepted the claims of Cogadh Gaedhil re Gallaibh at face value.
Brian did not free Ireland from a Norse (Viking) occupation, simply because it was never conquered by the Vikings. In the last decade of the 8th century, Norse raiders began attacking targets in Ireland and, beginning in the mid-9th century, these raiders established the fortified camps that later grew into Ireland's first cities: Dublin,Limerick, Waterford, Wexford, and Cork. Within only a few generations, the Norse citizens of these cities had converted to Christianity, intermarried with the Irish, and often adopted the Irish language, dress and customs, thus becoming what historians refer to as the 'Hiberno-Norse'. Such Hiberno-Norse cities were fully integrated into the political scene in Ireland long before the birth of Brian. They often suffered attacks from Irish rulers, and made alliances with others. Rather than conquering Ireland, the Vikings, who initially attacked and subsequently settled in Ireland, were, in fact, assimilated by the Irish.
Wives and Children Brian's first wife was Mór, daughter of the king of Uí Fiachrach Aidne of Connacht. She is said to have been the mother of his sons Murchad, Conchobar and Flann. Later genealogies claimed that these sons left no descendants, although in fact Murchad's son Tadc is recorded as being killed at Clontarf along with his father and grandfather.
Echrad daughter of the king of Uí Áeda Odba, an obscure branch of the southern Uí Néill, was the mother of Tadc, whose son Toirdelbach and grandson Muirchertachrivalled Brian in power and fame.
Brian's most famous marriage was with Gormflaith, sister of Máel Mórda of Leinster. Donnchad, who had his half-brother Tadc killed in 1023 and ruled Munster for forty years thereafter, was the result of this union.
Brian had a sixth son, Domnall. Although he predeceased his father, Domnall apparently had at least one surviving child, a son whose name is not recorded. Domnall may perhaps have been the son of Brian's fourth known wife, Dub Choblaig, who died in 1009. She was a daughter of King Cathal mac Conchobar mac Taidg of Connacht.
Brian had at least three daughters but their mothers are not recorded. Sadb, whose death in 1048 is recorded by the Annals of Innisfallen, was married to Cian, son ofMáel Muad mac Brain. Bé Binn was married to the northern Uí Néill king Flaithbertach Ua Néill. A third daughter, Sláni, was married to Brian's stepson Sitric of Dublin.
The descendants of Brian were known as the Ui Briain (O'Brien) clan, hence the surnames Ó Briain, O'Brien, O'Brian etc. "O" was originally Ó which in turn came from Ua, which means "grandson", or "descendant" (of a named person). The prefix is often anglicised to O', using an apostrophe instead of the Irish síneadh fada: "´". TheO'Briens subsequently ranked as one of the chief dynastic families of the country (see Chiefs of the Name).
In popular cultureDonal O'Neill, Sons of Death (1988), a historical novel about Brian Boru, told from the point of view of MelPatrick, a young nobleman at Brian's court. Uses the fictional device of the long-lost Brjánssaga as its source. Third in a series based on Irish history, beginning ca. 800 BC. (Vol 1 Crucible, Vol 2 Of Gods and Men).
The character of Miles O'Brien in the science fiction television show Star Trek: Deep Space Nine says that he is a direct descendant of Brian Boru in the 4th season episode "Bar Association".
In Ireland's largest amateur sporting organisation, the Gaelic Athletic Association, many clubs have been named after Brian Boru. These include Gaelic football, hurling,camogie and handball clubs, some now defunct, in London, Fermanagh (Kinawley), Tipperary (Clogheen Ladies, Annacarty-Donohill hurlers, and Brian Boru Camogie Club), Westmeath (Ballymore), Leitrim (Gorvagh), Pennsylvania (Philadelphia Hurling Club), Oregon (Portland Hurling Club), Cork (Shanballymore), Roscommon (Strokestown), Dublin (Clontarf, and Brian Boru’s Handball), Antrim (Cushendun) and Clare (Cratloe-Killaloe).