In Celtic mythology, Manawydan referred to Manannan mac Lir, as well as a son of Llyr and Penarddun.

Pryderi invited Manawydan (son of Llyr) to live with him in Dyfed after he married Rhiannon, Pryderi's mother. Soon, Dyfed turned into a barren wasteland and only Rhiannon (Pryderi's mother), Pryderi and his wife, Cigva, and Manawydan lived. Manaywdan and Pryderi, while out hunting, saw a white boar which they followed. Pryderi and his mother, Rhiannon, touched a golden bowl that the boar led them to and became enchanted. Manawydan and Cigva were unable to help them until they captured a mouse which was actually the wife of Llwyd, Rhiannon's enemy, and the spell was lifted.