Pryderi fab Pwyll is a prominent figure in Welsh mythology, the son of Pwyll and Rhiannon, and king of Dyfed after his father's death. He is the only character to appear in all Four Branches of the Mabinogi, although the size of his role varies from tale to tale. He is often equated with the divine son figure of Mabon ap Modron, while Jeffrey Gantz compares him to Peredur fab Efrawg, who is himself associated with the continental figure of Sir Percival de Galles.

Welsh mythology consists of both folk traditions developed in Wales, and traditions developed by the Celtic Britons elsewhere before the end of the first millennium. As in most of the predominantly oral societies Celtic mythology and history were recorded orally by specialists such as druids. This oral record has been lost or altered as a result of outside contact and invasion over the years. Much of this altered mythology and history is preserved in medieval Welsh manuscripts, which include the Red Book of Hergest, the White Book of Rhydderch, the Book of Aneirin and the Book of Taliesin. Other works connected to Welsh mythology include the ninth-century Latin historical compilation Historia Brittonum and Geoffrey of Monmouth's twelfth-century Latin chronicle Historia Regum Britanniae, as well as later folklore, such as the materials collected in The Welsh Fairy Book by William Jenkyn Thomas (1908).