Branwen ferch Llŷr; "Branwen, daughter of Llŷr" is a legendary tale from medieval Welsh literature and the second of the four branches of the Mabinogi. It concerns the children of Llŷr; Bendigeidfran, high king of Britain, and his siblings Manawydan and Branwen, and deals with the latter's marriage to Matholwch, king of Ireland. Matholwch's mistreatment of the British princess leads to a mutually destructive war between the two islands, the deaths of most of the principal characters, and the ascension of Caswallon fab Beli to the British throne. Along with the other branches, the tale can be found in the medieval Red Book of Hergest and White Book of Rhydderch. It is followed directly by the third branch, Manawydan fab Llŷr.

Brân the Blessed is a giant and king of Britain in Welsh mythology. He appears in several of the Welsh Triads, but his most significant role is in the Second Branch of the Mabinogi, Branwen ferch Llŷr. He is a son of Llŷr and Penarddun, and the brother of Brânwen, Manawydan, Nisien and Efnysien. The name "Brân" in Welsh is usually translated as crow or raven.