One of the Medieval kingdoms of Wales that existed between the fifth and tenth centuries AD, and named after its first king Glywys Cernyw; Glywys being the Brythonic or Old Welsh variant of the Latin Claudius.


Essentially comprising the land between the rivers Usk and the Tawe in south-east Wales, Glywysing included three main regions or cantrefs

  • Gwynllwg - in the east, bordering Gwent, centred on Allt Wynllyw
  • Gorfynedd - in the west, ruled from Llanilltud Fawr (or Llantwit Major)
  • Penychen - between the two, with its capital at Nant Pawl
  • History

    Its history remains obscure even by medieval Welsh standards. Most agree with the following initial succession of kings

    Some suggest that on his death Glywys divided the kingdom between his three sons with each succeeding to one of the principal cantref of the kingdom as follows,

    • Gwynllyw Farfog as king of Gwynllwg
    • Pawl ap Glywys as king of Penychen
    • Merchwyn Vesanus (Marcianus the Mad) as king of Gorfynedd
    Although even if this was the case Gwynlliw Farfog may have (or claimed to have) retained the overall kingship of the territory.

    Cadog Ddoeth, the son of Gwynlliw Farfog may have therefore ruled only Gwynllwg and Penychen (inherited the former from his father and the latter from his uncle)

    What is reasonably certain is that around the year 530 Cadog Ddoeth died without issue and bequeathed his kingdom to Meurig ap Caradog king of Gwent. Glywyssing remained part of Gwent until the time of Rhys ap Ithel in the mid eighth century, when he appears to have ruled ruled it as a seperate or possibly sub-kingdom of Gwent

    Whatever status Glywysing enjoyed at the time of Rhys ap Ithel the kingdom gradually reasserted its independence over the following decades and generated the following succession of kings;

    On Owain's death the kingdom seems to have been divided up between his three sons,

    By 950 Morgan had successfully re-united the kingdom and decided to honour the event by renaming it after himself, as Morgannwg.

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