Cantref Reservoir is the middle of the three reservoirs in the Taff Fawr valley in Wales. It was built by Cardiff Corporation Waterworks between 1886 and 1892, but since 1973 has been owned by Welsh Water. It is located in the Brecon Beacons National Park, mostly in the Powys unitary authority area and within the historic county boundaries of Breconshire. Part of the south west corner is in the Rhondda Cynon Taff unitary authority area. A public footpath crosses the dam and links with the Taff Trail and the paths.