Penychen was a possible minor kingdom of early medieval Wales and later a cantref of the Kingdom of Morgannwg. Penychen was one of three cantrefi that made up the kingdom of Glywysing, lying between the rivers Taff and Thaw, the other two being Gwynllwg and Gorfynydd. According to tradition, these cantrefi were created on the death of Glywys, the first king of Glywysing, when the kingdom was divided between his three sons: Pawl, Gwynllyw and Mechwyn. But our knowledge of the early history of the kingdom is very uncertain, being mainly sourced from medieval documents and traditional pedigrees.