According to Welsh legend, Madog was one of the sons of Owain, Prince of Gwynedd (North Wales). On the death of his father in 1170, Madog is supposed to have set sail with a shipload of companions on a westward course. He is reputed to have reached America, left some of his party, returned to Wales for additional compatriots, and repeated the crossing of the Atlantic. As a result of this story the belief grew up that somewhere in North America there existed a tribe of white Indians who spoke perfect Welsh, produced supposedly by the inter-marriage of the original Welsh seafarers and indigenous inhabitants as in Patagonia today.
As for Madog himself, there is no historical proof of his existence. A medieval poem refers to Madog ab Owain Gwynedd as a sailor; and, quite probably, the Welsh Tudors used the story for propaganda purposes to challenge Spanish claims to the New World. Romantically, however, and particularly in view of the maritime traditions of North Wales, it is perhaps fitting that this research vessel should bear the name of Madog, the legendary marine explorer of an earlier age.