The Carmarthen by-election of 1957 in Carmarthenshire, Wales, was notable for resulting in the nadir of the British Liberal Party and for being the first election in the United Kingdom in which two women competed for the same seat. The other candidate who ran for the seat was Jennie Eirian Davies of Plaid Cymru. The Conservatives did not run a candidate. This was the second to last by-election in Great Britain in which they did not stand, the last being the unusual circumstances of the Bristol South East by-election, 1963.