Donnchad Ua Cerbaill or Donnchadh Ó Cearbhaill, king of Airgíalla, fl. c. 1130–1168. Ua Cerbaill was a supporter of the Irish religious reform movement of the 12th century. He was a close associate of Saint Malachy, and with him founded Mellifont Abbey, the first Cistercian abbey to be built in Ireland. He was also responsible for foundations by the Arrouaisian order at Louth, Knock Abbey and Termonfeckin. Saint Malachy's brother Christian (Gilla Críst Ua Morgair) served as Bishop of Clogher in the Ua Cerbhaill kingdom from 1126 to 1138 at the time Donnchad came to power.