Diarmait Cléirech Ó Briain

Diarmait Cléirech Ó Briain (died 1 June 1313), surnamed the Clerk, was the son of Donnchad mac Briain and grandson of Brian Ruadh. In 1311, after the death of King Donnchad mac Toirdhealbhach, Richard de Clare imposed him as king of Thomond and had him inaugurated.

William de Burgh, who backed the rival claim of Muircheartach Ó Briain, resisted him. Diarmait died suddenly on 1 June 1313 and was buried in the Franciscan church, leaving Thomond to renewed civil war.