Dinefwr was a local government district of Dyfed, Wales from 1974 to 1996. It was named after Dinefwr Castle which was the court of the House of Dinefwr and one of the three principal royal courts of Wales with Aberffraw and Shrewsbury. It was formed by the merger of the borough of Llandovery, the urban districts of Ammanford, Cwmamman and Llandeilo along with Llandeilo Rural District, from the administrative county of Carmarthenshire. See also