where does the last name obrien come from
O'Brien dynasty The O'Brien dynasty (Classical Irish Irish: Ua Briain, (Modern Irish Ó Briain, IPA: /oːˈbʲɾʲiənʲ/), genitive Uí Bhriain, IPA: /iːˈβʲɾʲiənʲ/) are a royal and noble house founded in the 10th century by Brian Boru of the Dál gCais or Dalcassians. After becoming King of Munster, through conquest he established himself as Ard Rí na hÉireann (High King of Ireland). Brian's descendants thus carried the name Ó Briain, continuing to rule the Kingdom of Munster until the 12th century where their territory had shrunk to the Kingdom of Thomond which they would hold for just under five centuries.