The Carmarthen by-election of 1957 in Carmarthenshire, Wales, was notable for resulting in the nadir of the British Liberal Party.

Caerfyrddin is a proposed parliamentary constituency in Wales to return one Member of Parliament (MP) to the House of Commons of the Parliament of the United Kingdom, from the next general election. It previously existed between 1542 and 1997 under the English version of the name, Carmarthen. It was named Carmarthen Boroughs from 1832 to 1918; between 1997 and 2024 it was divided between Carmarthen East and Dinefwr constituency and Carmarthen West and South Pembrokeshire.