Ultan was the uncle of St Brigid, a disciple of St Declan, bishop of Ardbraccan and was noted for illuminating the writings of St Brigid. Ultan founded a school, educating and feeding its poor students. He has been described as "the great sinless prince in whom the little ones are flourishing: the children play greatly round Ultan of Ardbraccan." The Yellow Plague attacked adults more than children. In many places through the country children were left orphaned, helpless and starving. Ultan collected as many children as he could find and brought them to his monastery. He often had as many as 150 children. Ultan ended his days in 653 on one of the Aran Islands.
He is the Patron Saint of paediatricians and a children's hospital in Dublin.