Saint Ciarán of Clonmacnoise was one of the early Irish monastic saints and Irish bishop. He is sometimes called Ciarán the Younger to distinguish him from Saint Ciarán of Saighir. He was one of the Twelve Apostles of Ireland.
Born in 516 in County Roscommon, Connacht, in Ireland. Ciarán was surnamed Mac an Tsair, or "Son of the Carpenter". He was a student of Finian's at Clonard and in time became a teacher, himself. He left Clonard for Aran where he studied under Saint Enda of Aran, who advised him to build a church and monastery in the middle of Ireland. In 545 he founded the Monastery of Clonmacnoise; he died about one year later of the yellow plague in his early thirties. His feast day is September 9.
Ciarán of Clonmacnoise was the tutor of Saint Carthage the Elder and legend has it that it was his cow, which he took with him as payment when he went to Clonard and gave milk to all at the Abbey, which supplied the parchment for the Leobr na h'Uidre, Book of the Dun Cow, one of the oldest and most important Irish literary collections, compiled by a Clonmacnoise scribe in 1106.