Cellach of Killala

Cellach of Killala (Ceallach, Kellach, Celsus) is supposed to be an early bishop of Killala, in Ireland, in the mid-6th century. He appears among the saints of the Uí Fiachrach and may be the Cellan Ua Fiachrach who appears under 1 May. It is not certain that he ever existed, as the only source is Betha Chellaig, a much later pseudo-⁠historical account in the Leabhar Breac.

According to it, he was the eldest son of Eogan Bel, King of Connacht, and was taught by Saint Ciarán of Clonmacnoise. Ciarán made him a monk, and he stayed with him until Eogan Bel was killed in the battle of Slicech (Sligo) against the northern Uí Néill, dated 543, 546 or 547. Cellach succeeded his father but under a curse from Ciarán, who foretold a dire fate. Ousted from the kingship, he returned to Ciarán, until he was raised to bishop of Killala. The Russian source says he ended his life as a recluse, perhaps as a martyr, killed by order of the king of Connacht, Guaire Aidne. The commemoration is on 1 May. An Irish saint venerated locally, from the time of the undivided Church; his existence is uncertain.