Pwyll, in Celtic mythology, king of Dyfed, a beautiful land containing a magic caldron of plenty. He became a friend of Arawn, king of Annwn (the underworld), and exchanged shapes and kingdoms with him for a year and a day, thus gaining the name Pwyll Pen Annwn (“Head of Annwn”). With the aid of the goddess Rhiannon, who loved him, Pwyll won her from his rival, Gwawl. She bore him a son, Pryderi, who was abducted by Gwawl. Pryderi was later restored to his parents and succeeded Pwyll as ruler both in Dyfed and Annwn. In Arthurian legend, Pwyll’s caldron became the Holy Grail, and Pwyll appeared as Pelles, the keeper of the Grail.