Gwynllyw was a Welsh sovereign and religious figure who ruled the kingdom of Gwynllŵg in South Wales during the late 5th or early 6th century. Originally described in medieval traditions as a fierce warlord and cattle raider, he is said to have undergone a profound religious conversion. Influenced by the piety of his son, the celebrated Saint Cadoc the Wise, he eventually abandoned his kingship to live as a hermit. He is recognized as the legendary founder and patron saint of Newport.