Fachtna, also known as Fachanan or Mac Mongach, was a 6th-century Irish Christian leader. Born at Tulachteann, he received his education under Saint Ita and studied at Gougane Barra, while also being taught by Brendan the Navigator. He is widely recognized for establishing the monastery and school at Rosscarbery in County Cork, as well as founding a monastic site on Molana island. Due to his skill in speech, he was frequently referred to as Fachtna the Eloquent.