Seiriol was a 6th-century saint and abbot who lived in North Wales. The son of King Owain Danwyn of Rhos, he was the younger brother of Kings Cynlas and Einion. He established a religious cell at Penmon Priory on Anglesey before eventually retiring to Ynys Seiriol, also known as Puffin Island. Because he traveled in the opposite direction of his friend Saint Cybi, facing away from the sun, he earned the epithet Seiriol Wyn, which means Seiriol the Fair.