Cynllaith or Cynllaeth was a commote (Welsh: cwmwd) of north east Wales in the cantref of Welsh: [[Swydd y Waun]]|italic=no (later Chirkland) which was once part of the Kingdom of Powys and later part of the smaller kingdom of Powys Fadog.[1]
Cynllaith, or at least the part of it called Cynllaith Owain, was part of the inheritance of Owain Glyndŵr in 1370.[2] The titles Baron of Glyndyfrdwy and Lord of Cynllaith Owain were used by the dispossessed former ruling family of Powys Fadog before Owain was proclaimed Prince of Wales in 1400.[3]
The episode "Monk's Hood" of the Cadfael Chronicles includes a scene in a Welsh court in Llansilin within this commote.