Fedelmid mac Crimthainn was an eighth-century Irish ruler and religious leader who served as the King of Munster from 820 to 846. A member of the Céli Dé, he held significant ecclesiastical positions, acting as the abbot of both Cork and Clonfert Abbeys, and potentially serving as a bishop. His reign was characterized by extensive military campaigns and the establishment of the Law of St. Patrick in Munster. He is remembered as both a powerful sovereign and a holy man, eventually being commemorated as a saint.