Merthyr Tydfil County Borough is located in the historic county of Glamorgan in Wales and takes its name from its largest town. The county borough covers an area of 111 km2 (43 sq mi) and had a population of approximately 60,400 in 2020. There are ten structures on the list of twelve Grade II* listed buildings in Merthyr Tydfil. Two viaducts constructed as part of the Brecon and Merthyr Railway both straddle the borders of neighbouring communities so have separate designations for each of these locations.