Arianrhod ("Silver Wheel") was a Welsh goddess of the Mabinogion's Fourth Branch, daughter of Dôn (the Welsh Danu) and sister of Gwydion. The narrative concerning her is among the more curious in medieval Welsh literature. She had been called as candidate for the office of foot-holder to her uncle Math, king of Gwynedd — an office that had to be held by a virgin, on whose lap the king kept his feet when not at war. Tested for her virginity by the magical wand, she was revealed not to be the virgin she had claimed: she gave birth on the spot to a fully formed boy (Dylan, who immediately fled to the sea and became a sea-divinity) and to a small embryonic mass that her brother Gwydion took up in a cloth and concealed in a chest at the foot of his bed. From this concealed embryo grew a second boy, whom Gwydion raised in secret.

Arianrhod, ashamed by the public revelation, refused to acknowledge her son. She laid three curses upon him: that he should never have a name unless she gave it; that he should never have arms unless she gave them to him; that he should never have a wife of any race now upon the earth. Gwydion, by various magical deceptions, defeated all three curses (he tricked her into naming the boy Lleu Llaw Gyffes, "the Bright One of the Skillful Hand," while she watched him hit a bird with a stone; he tricked her into arming the boy by a sham invasion that required arms be given; and he and Math made the boy a wife from the flowers of the oak, the broom, and the meadowsweet — Blodeuwedd, who would have her own subsequent narrative). Arianrhod was outwitted at every step; the boy Lleu corresponds linguistically to the Irish Lugh (treated above), and the Welsh narrative is plainly an alternative version of the same Indo-European mythological complex about the Bright One's birth and arming.