In Welsh mythology, Gwydion is a magician appearing prominently in the Fourth Branch of the Mabinogi and the ancient poem Cad Goddeu. He is the brother of Gilfaethwy and Arianrhod, and the nephew of Math fab Mathonwy. In the Mabinogion he is called the son of the goddess Dôn, making it likely he is an euhemerized god or demi-god. The name Gwydion may mean 'To Speak Poetry'.