Powys Fadog or Powys Maelor was the northern portion of the former princely realm of Powys which split in two following the death of Madog ap Maredudd of Powys in 1160. The realm was divided under Welsh Law, with Madog's nephew Owain Cyfeiliog inheriting the south (see Powys Wenwynwyn) and his son Gruffydd Maelor I who inherited the north.
Gruffydd Maelor I received the cantrefi of Maelor and Ial as his portion and later added Nanheudwy, Cynllaith, Glyndyfrdwy and Lower Mochnant. This northern realm became known as Powys Fadog after 1191.
Princes of Powys Fadog
- 1160–1191 Gruffydd Maelor
- 1191– 1236 Madog ap Gruffydd Maelor
- 1236–1269 Gruffydd II ap Madog, Lord of Dinas Bran
- 1269–1277 Madog II ap Gruffydd, Lord of Dinas Bran
Madog II was defeated and killed in war with Gwynedd. His brother and heir was forced to accept the overlordship of Llywelyn ap Gruffydd.
- 1277–1289 Gruffydd Fychan I ap Gruffydd, Lord of Dinas Bran
After the defeat of his ally Llywelyn ap Gruffydd in the wars of independence all of Powys Fadog was incorporated into the counties of Denbighshire and Flintshire joining with neighbouring cantrefi formerly parts of eastern Gwynedd. The family received pardons and retained much reduced lands as Marcher Lords.
- 1289–1304 Madog Crypl, Lord of Glyndyfrdwy and Lord of Cynllaith Owain
- 1304–c.1325 Madog Fychan, Lord of Glyndyfrdwy and Lord of Cynllaith Owain
- c.1325–1369 Gruffydd Fychan II, Lord of Glyndyfrdwy and Lord of Cynllaith Owain
- 1359–c.1416 Owain ap Gruffydd, Lord of Glyndyfrdwy and Lord of Cynllaith Owain
Owain ap Gruffydd rose in revolt against the English crown in 1400 and proclaimed himself Prince of Wales. He became more widely known as Owain Glyndŵr. After his death at least one of his sons survived him. What became of them is not known.
- 1416–? Maredudd ab Owain Glyndŵr