Fiachan of Lismore was an early Irish monk from the Munster region who died in 630. As a disciple of Mo Chutu (Carthagh the younger) at the monastery in Lismore, he was recognized for his profound obedience and spiritual virtues. Historical accounts, including the Life of St. Mochuda, identify him as one of the twelve highly esteemed disciples within the monastic community, noted for a level of piety that inspired his mentor.