Gwrtheyrnion

Gwrtheyrnion or Gwerthrynion was a commote in medieval Wales, located in Mid Wales on the north side of the River Wye. For most of the Middle Ages, its rulers operated independently of other powers, but it was sometimes associated with the cantref of Maelienydd and the Kingdom of Powys, and, in the Norman era, with the region known as Rhwng Gwy a Hafren. It is said to have taken its name from the legendary king Vortigern (Welsh: Gwrtheyrn), and for a time was part of an independent regional kingdom.

According to the 9th-century Historia Brittonum, Gwrtheyrnion, here Latinised Guorthegirnaim, was named for Vortigern (Welsh: Gwrtheyrn), a legendary 5th-century King of Britain.John Edward Lloyd considers this derivation accurate. Generally, its boundaries were the cantrefi of Arwystli to the north, Maelienydd (in its restricted sense) to the east, Elfael to the southeast, and Buellt to the southwest. It also controlled the commote of Cwmwd Deuddwr on the west of the Wye; together they formed a cantref.

Around 800, Gwrtheyrnion formed part of a minor regional kingdom with Buellt, situated across the Wye. Later medieval lists of commotes and cantrefs more generally associate it with territories on the north side of the Wye; some, but not all, tie it to the cantref of Maelienydd. Others tie it instead to Arwystli, though this is evidently the result of a scribal error. The historical centre of Gwrtheyrnion was Rhayader, from which it is thought the traditional county of Radnorshire was named.

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