An early legendary King of Powys. The King of Brecknock in Welsh tales. He might have been a historical figure - a fifth-century British chieftain, thought to be the father of up to sixty-three saints, including Saint Gwladys.

The Triads mention him as the father of Urien of Rheged's mother Nefyn, and as one of the "three saintly lineages of the Island of Britain".

In the life of Saint Cadoc, his wife Gwladys is abducted by King Gwynnlyw of Glamorganshire (Gwynnlym Filwk), and she is later lusted after by Arthur.