A historical sixth-century king of Gwynedd mentioned in several Welsh texts. The Latin version of his name is Maglocunus ('Hound Prince'), and a certain "Maglocune" is berated by Gildas in his De Excidio Britanniae. The Annales Cambriae says that he died in 547 from the plague.

The son of Clutarius, he has been tenously identified with Melkin. In the Welsh Triads, he appears as one of Arthur's chief elders. He has two sons named Rhun and Alser. In another Welsh poem, Taliesin and Myrddin mourn the deaths of many warriors who died in a battle against Maelgwn.