Mountain Ash is a town and former community in the Cynon Valley, within the County Borough of Rhondda Cynon Taf, Wales, with a population of 11,230 at the 2011 Census, estimated in 2019 at 11,339. It includes the districts and villages of Cefnpennar, Cwmpennar, Caegarw, Darranlas, Fernhill, Glenboi and Newtown, all within the historic county boundaries of Glamorgan. Aberdare lies about 4.5 miles (7.2 km) north-west, Cardiff 19 miles (31 km) south-east, and Penrhiwceiber a mile to the south-east. It divides into two communities : West covers the town centre and the districts of Miskin, Darranlas, Fernhill and Glenboi, and East the districts of Cefnpennar, Cwmpennar, Caegarw and Newtown.