Rhwng Gwy a Hafren

Rhwng Gwy a Hafren (English: Between Wye and Severn) was a region of medieval Wales, located in the Welsh Marches between Powys to the north and Brycheiniog to the south.

[3] The small commotes of Ceri in Maelienydd and Cwmwd Deuddwr north of Buellt (and also across the Wye) were located in this area and appear in some sources, but are not included in the lists of divisions.

[5] The rulers of this kingdom did not trace their descent from the royal line of Powys, but from Pascent or Pasgen, a reputed son of the early king Vortigern.

Norman authority suffered a serious reverse within fifty years with the emergence of Cadwallon ap Madog and his younger brother Einion Clud as Princes of Elfael and Maelienydd.

Throughout the 13th century the territory as described was gradually reoccupied by the English Marcher Lords, and Roger Mortimer built a castle at Cefnllys to consolidate his gains in Maelienydd.

The Red Book of the Exchequer, a mainly 13th-century English compilation of landholdings, mentions a region of seven cantrefs "between Severn and Wye" that had been known as Kenthlebiac during the time of Rhys ab Owain of Deheubarth.

[6] The Domesday Book of 1086 refers to a place called Calcebuef, which rendered ten shillings; one editor suggests this is a corruption of Cynllibiwg and that it derives ultimately from the name of Saint Cynllo.