Powys Fadog or Lower Powys is the northern portion of the former princely realm of Powys, which splits in two following the death of Madog ap Maredudd of Powys in 1160.

The realm is divided under Welsh Law, with Madog's nephew Owain Cyfeiliog inheriting the south (see Powys Wenwynwyn) and his son Gruffydd Maelor who inherits the north.