Cynon Valley was a constituency in Wales, of the House of Commons of the UK Parliament from 1983 to 2024. Its last MP from 2019 to 2024 was Beth Winter of the Labour Party. The Cynon Valley Senedd constituency was created with the same boundaries in 1999 (as an Assembly constituency). The constituency was abolished as part of the 2023 Periodic Review of Westminster constituencies and under the June 2023 final recommendations of the Boundary Commission for Wales. Its wards were split between Merthyr Tydfil and Aberdare, and Pontypridd.

Boundaries

1983–2010: The Borough of Cynon Valley. 2010–2024: The Rhondda Cynon Taff County Borough electoral divisions of Aberaman North, Aberaman South, Abercynon, Aberdare East, Aberdare West/Llwydcoed, Cilfynydd, Cwmbach, Glyncoch, Hirwaun, Mountain Ash East, Mountain Ash West, Penrhiwceiber, Pen-y-waun, Rhigos, and Ynysybwl. The constituency encompasses the towns of Aberdare, Mountain Ash, Cilfynydd, Abercynon and Hirwaun.

Members of Parliament

Elections

Elections in the 1980s

Elections in the 1990s

Elections in the 2000s

Elections in the 2010s

Of the 81 rejected ballots: