O Brien - Irish / Ua Briain. An anglicized form used by the Heberian Dal gCais Ui Bloid Ui Turlough Ui mBriain Sept / Family branch, who had their kingdom in Thomond / Tuaisceart Mhumhain / Northern Munster who were based in Co. Clare and the surrounding regions in Co. Limerick, Co. Tipperary and Co. Waterford. They are directly descended from *105.Brian "Boru" - of the Tributes, the Dalcassian King of Thomond, 41st King of Munster and 170th High King of Ireland in 1002 AD. The Ui Turlough Sept were descended directly from *98.Turlough who was also the father of 99.Ailgenan the ancestor of the O Mearas / Ui Meadhra who was also from the Ui Bloid Sept, descended from *92.Blood / Blod  the oldest son of *91.Cas the King of Thomond who was in turn descended from *85.Cormac "Cass" the 2nd King of Munster who was the second eldest son of *84.Ailill "Olomm" the 1st King of Munster in the 2nd Century AD. He was descended in turn from *37.Heber "Fionn"/ of Fair Complexion the Scythian Celtic Gaelic Milesian joint 1st King of Erinn the direct ancestor of all of the Heberian Septs. *91.Cas along with his 12 sons are the ancestors of all the Dal gCais (People of *91.Cas) in Thomond. They were Chiefs in Co. Waterford in the south - east of Munster Province where they were also Kings and Princes, English appointed Earls and Barons in Co. Clare in the north - west of the Munster, Kings and Chiefs in Co. Tipperary in Aur Mhumhain / Ormond the north - east of Munster Province, Kings in Co. Galway in Southern Connacht, Princes and Kings in Co. Limerick in the mid - north - west of Thomond.

      In 976 AD, due to the Viking disruptions, the Dal gCais Septs in Thomond were well and truly on the ascendant, and *105.Brian "Boru" from the Ui Turlough Sept became the King of Thomond. In 978 AD he defeated and slew 109.Molloy / Maelmuad the Heberian Eoghanacht Ui Raithlind 40th King of Munster in battle who had been involved in the previous death of his brother, *105.Mahon the 39th King of Munster, and he became the 41st King of Munster. He then attempted to unite the ravaged Irish Tuaths / Family regions, to stop any further Viking incursions, which had also destroyed the basic fundamentals of the Irish Brehon Law. 104.Malachy 11 / Mael Sechlainn the Heremonian Ui Cobhthaigh Dal Cuinn  "Southern" Ui Niaill Clann Cholmain 40th King of Meath and 169th King of Ireland whose territory was in the south - west of Northern Leinster, along with the Heremonian Ui Cobhthaigh Dal Cuinn Ui Briuin kingdom of Breifne in the west in the Connacht Province, all submitted to *105.Brian. In 1002 AD he then became the 170th High King of Ireland who was then to end the Viking advance in a terrible battle in 1014 AD at Clontarf in Co. Dublin in the north - east of Southern Leinster. The Ua mBriain surname was first used by his great - grandson, *107.Teigue Ua Briain, and *111.Donough "Cairbre" Ua Briain the son of *110.Donal "Mor" O Briain the Dalcassian King of Munster in respect of 105.Brian’s wish for all the Irish people to use their descent from their ancestors as their surnames. The Ui mBriain Tuath / Family region, later on split into the O Briens of Aherlow, the O Briens of Co. Waterford and the O Briens of Arra in the north of Co. Tipperary and of Co. Limerick. They had their Tromra Castle near Quilty in Co. Clare and another at Carrigogunnell in Co. Limerick. In 1542 AD on July 1st; 121.Murrough "The Tánaiste" Ua Briain accepted English titles and the re - grant of the Dal gCais Sept's territory to himself personally under English Law from Henry V111, although it was against the Irish Brehon Law, and he became the 1st English appointed Earl of Thomond and the 1st English appointed Baron of Inchiquin. His nephew, 123.Donough O Brien was made the 1st English appointed Baron of Ibricken (This was to see the end of the Dal gCais Sept as an Irish Tuath / Family region, as the Dal gCais Septs then in reality were basically left leaderless) What was then the main leading Sept then became the English appointed Earls and Marquises of Thomond, English Earls of Inchiquin, English Barons of Ibrackan, English Barons of Burren, English Viscounts of Clare and the English Barons of Moyarta. These leading branches of the Septs were to fore sake their Irish Gaelic heritage and their Irish people to hold onto the land in Co. Clare personally, and to do this they also had to become non - Catholic. They then married English women to gain financial reward to uphold their English titles and Estates until eventually most of their English titled main branches were to die out. "The O Brien" at present is Conor O Brien. Ancestors - *105.Briain (Ui mBriain) the King of Thomond, 41st King of Munster and 170th High King of Ireland, *104.Kennedy / Ceaneidigh, *103.Lorcan / Fingin, *102.Lachtna,*101.Corc, *100.Anluan, *99.Mahon, *98.Turlough / Toirdhealbhach (Ui Turlough), *97.Cathal, *96.Aodh "Caomh" the King of Munster, *95.Conall, *94.Eochy / Eochaidh "Baill Dearg," *93.Cairthenn "Fionn Oge Mor," *92.Blood / Blod (Ui Bloid), *91.Cas (Dal gCais) the King of Thomond, *37.Heber "Fionn (Heberians).