Saint Aerdeyrn (c. 6th century) was a semi-legendary pre-congregational saint of Wales.
He was a descendant of Vortigern, making him related to the royal house of Powys.
He was the brother of Saint Edeyrn and Elldeyrn[1] with whom he is oft associated.
His name was derived from the Celtic word for Prince.
[2] He built churches in Glamorgan[3] and he is the patron Saint of Llanelldeyrn, Wales.