Merthyr Tydfil is located in Cardiff city, United Kingdom at the 51.7479, -3.3778 coordinates. Distance from Merthyr Tydfil to other cities. are listed below, click on the city name to find distance between. Distance from Merthyr Tydfil to Swansea 41 km, to Newport 32 km, to Rhondda 11 km. The green marker indicates the location of Merthyr Tydfil.