Dylan (or Dylan Eil Ton; sea in Welsh) is a sea-god in Welsh Celtic mythology, a son of Arianrhod and Gwydion. He was killed by his uncle, Govannon, who didn't know who he was. He is sometimes said to be a god of darkness.

Dylan was the first of the two sons born to Arianrhod - the second being Llew Llaw Gyffes. Since the moment of his birth the golden-haired Dylan was a creature able to swim in the ocean like a fish, and he therefore received the epithet Eil Ton (Son of the Wave). It was said that his death caused all the waves of the sea to mourn his loss.