Cynheidre Colliery was a coal mine located in the Gwendraeth valley, in Carmarthenshire, South Wales. Opened in 1954, it closed in 1989. Cynheidre was developed by the National Coal Board as one of the West Wales "super pits" alongside Abernant Colliery in the River Amman valley, a post-World War II investment intend to keep economic coal mining a viable industry in the area. Created to exploit 196 square miles (510 km2) of deep lying anthracite seams, it was envisaged to eventually encompass the working of the drift mines at the Great Mountain Colliery and Pentremawr.