Carmarthen by-elections are the by-elections held on occasion for the British House of Commons constituency of Carmarthen in North Wales:
1878 Carmarthen Boroughs by-election 1882 Carmarthen Boroughs by-election 1924 Carmarthen by-election 1928 Carmarthen by-election 1941 Carmarthen by-election 1957 Carmarthen by-election 1966 Carmarthen by-election
See also Carmarthen (UK Parliament constituency) List of United Kingdom by-elections