Llanddewi Ystradenni is a community in Powys, Wales. The population of the Community at the 2011 census was 310.
Centred on the village of Llanddew, within the community is the motte and bailey defensive fortification of Buddugre Castle, overlooking the Afon Ithon. Coordinates: 52°18′0″N 3°18′0″W / 52.30000°N 3.30000°W