Donnchad mac Briain Ó Briain

Donnchad mac Briain Ó Briain (died 1284), eldest son of Brian Ruadh, claimed Thomond after his father's execution by Thomas de Clare in May 1277. In 1278 they raided de Clare's lands, but civil war with their cousin Toirdhealbhach Mór forced them back into de Clare's alliance. In 1280 de Clare partitioned Thomond between the rivals, and fighting soon resumed.

In 1284 Donnchad was betrayed by his own men and killed while bathing in the Fergus near Clare Castle. His son was Diarmait Cléirech Ó Briain.