Maelgwn Gwynedd (died c. 547) was King of Gwynedd for an unspecified period in the early 6th century. More formally his name was Maelgwn ap Cadwallon (English: Maelgwn son of Cadwallon), also known as Maelgwn Hir (English: Maelgwn the Tall). He was father of Rhun "Hîr".
The evidence suggests that he held a pre-eminent position among the kings in Wales and in parts of northern Britain known as 'The Old North' (Welsh: Yr Hen Ogledd). Maelgwn was a generous supporter of Christianity, making donations to found churches throughout Wales, far beyond the bounds of his own kingdom.
The history of Brythonic Gwynedd begins with the conquest of the Gaelic peoples of northern Wales by Maelgwn's great-grandfather Cunedda, with the conquest finally completed by Maelgwn's father Cadwallon. Maelgwn was the first king to enjoy the fruits of his family's conquest and he is considered the founder of the medieval kingdom's royal family. He is thus most commonly referenced by appending the name of the kingdom to his own: Maelgwn Gwynedd.
By tradition, his llys (English: royal court, literally hall) was located at Deganwy, in the Creuddyn peninsula of Rhos. Tradition also holds that he died at nearby Llanrhos, and was buried there. Other traditions say that he was buried at Ynys Seiriol (English: Island of St. Seiriol, Puffin Island), off easternmost Anglesey. There are no historical records to confirm or deny these traditions.
Historical records of this early era are scant. Maelgwn appears in the royal genealogies of the Harleian genealogies, Jesus College MS. 20, and Hengwrt MS. 202. His death in a "great mortality" of 547 is noted in the Annales Cambriae. Tradition holds that he died of the 'Yellow Plague' of Rhos, but this is based on one of the Triads that was written much later. The record says only that it was a "great mortality".
Maelgwn was a generous contributor to the cause of Christianity throughout Wales. He made donations to support Saint Brynach in Dyfed, Saint Cadoc in Gwynllwg, Saint Cybi in Anglesey, Saint Padarn in Ceredigion, and Saint Tydecho in Powys. He is also associated with the foundation of Bangor, but hard evidence of this is lacking. In his 1723 Mona Antiqua Restaurata, Henry Rowlands asserts that Bangor was raised to an episcopal see by Maelgwn in 550, but he provides no source for the assertion.
The only contemporary information about the person is provided by Gildas, who includes Maelgwn among the five British kings who he condemns in allegorical terms in his De Excidio et Conquestu Britanniae. He says Maelgwn held a regional pre-eminence among the other 4 kings, going on to say that he overthrew his maternal uncle (Latin: avunculus) to gain the throne; that he had taken up life as a monk but then returned to the secular world; that he had been married and divorced, then remarried to the widow of his nephew after being responsible for his nephew's death; and that he was tall.
Gildas refers to Maelgwn by the older form of his name, Maglocunus (or Maglocune). This was successively softened down into Mailcon or Mailcun, to become Maelgwn. Maglo- in Brythonic means a prince or hero, equivalent to the Irish mál and different from Brythonic moel (bald, bare) and Irish mael (tonsured, servant). The early Brythonic cu has become Welsh ci, genitive or nominative plural cwn, the word for hound or dog, with a positive military connotation in the sense of the dangerous hound or hounds of war.
Read more about Maelgwn Gwynedd: High King, Gildas, Literary Record, Literary Misinformation