The Black Mountain () is a mountain range in South and West Wales, straddling the county boundary between Carmarthenshire and Brecknockshire (the latter currently administered as part of the unitary authority of Powys) and forming the westernmost range of the Brecon Beacons National Park. Its highest point is Fan Brycheiniog at 802 metres or 2,631 ft. The Black Mountain also forms a part of the Fforest Fawr Geopark.