Caerfyrddin (Welsh: [kairˈvərðɪn]), also known as Carmarthen, is a constituency of the House of Commons in the UK Parliament, first contested at the 2024 United Kingdom general election, following the 2023 Periodic Review of Westminster constituencies.

Because the seat contained mining areas in the valley of the River Gwendraeth (until the 1980s), much countryside and a high proportion of Welsh speakers, it was fertile territory for the Labour Party, the Conservatives and Plaid Cymru alike.

Carmarthen is notable as the first constituency to elect a Plaid Cymru MP, Gwynfor Evans, at a 1966 by-election.

Evans was later involved in one of the closest General Election results ever in February 1974, when he lost to the Labour candidate by only three votes.

[4][5] The constituency also shot to fame in the following election in October 1974 as the only seat in the country to see its turnout rise on that of February 1974.