Town (pop., 1991: 13,524), administrative centre of the county of Carmarthenshire, southern Wales.
It lies on the Afon Tywi above the mouth of the Bristol Channel . Both the Romans and Normans built strongholds there. An Augustinian priory dating from the Norman period once housed the Black Book of Carmarthen ( 0441; 1250), which is the oldest Welsh manuscript extant.