Ailerán, also known as Ailerán sapientis (Ailerán the Wise) was an Irish scholar and saint who died 29 December, 664 or 665. His feast day is December 29. The date of birth isn't recorded.
He was a good student at the school Clonard. His early life is not recorded but we know that he was attracted to Clonard by the fame of Saint Finnián and his disciples. He hasn't any patronage.
He became lector of the school in 650. According to John Colgan, an Irish Franciscan, Alierán wrote "Fourth Life of Saint Patrick", "Ancestry of Our Lord Jesus Christ" and published other texts.