Carmarthen is the county town of Carmarthenshire and a community located in Wales, United Kingdom. Situated on the River Towy, it lies approximately 8 miles (13 km) north of its estuary in Carmarthen Bay. According to the 2021 census, the community had a population of 14,636, while the built-up area recorded a population of 16,455.
The town stands on the site of an ancient Roman settlement and holds a claim to be the oldest town in Wales. During the Middle Ages, it consisted of twin settlements known as Old Carmarthen, centered around Carmarthen Priory, and New Carmarthen, located near Carmarthen Castle; these two areas were merged into a single borough in 1546.
Historically, Carmarthen was the most populous borough in Wales from the 16th to the 18th centuries. During this period, it was described by William Camden as the "chief citie of the country" before being overtaken in size by the mid-19th century due to the expansion of settlements within the South Wales Coalfield.