Y Gorddwr (Welsh for 'The Upper Water'; also known as Corddwr) was a medieval commote (cwmwd) in the cantref of Ystlyg in the Kingdom of Powys.
He was related to them through his mother, Margaret, who was a sister of Thomas Corbet, the baron of Caus at the time, this added weight to his claim.
[4] He inherited his mother's lands in Y Gorddwr in 1246, and appropriated more in 1252 while King Henry III was in dispute with Simon de Montfort.
[4] In 1257, before Gruffydd could relinquish the land in Y Gorddwr, Llywelyn ap Gruffudd had taken his territory in Powys and forced him into exile in England.
King Henry still insisted that he handed the territory he held in Y Gorddwr over to Corbet,[4] so in 1263 Gruffydd transferred his allegiance to Llywelyn,[7] and his lands were returned to him.