Merthyr Tydfil and Rhymney (UK Parliament constituency)

Merthyr Tydfil and Rhymney (Merthyr Tudful a Rhymni) was a constituency represented in the House of Commons of the UK Parliament. It was established for the 1983 general election.

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 for the 2024 United Kingdom general election. Its wards were split between Blaenau Gwent and Rhymney, and Merthyr Tydfil and Aberdare.

Boundaries
1983–1997: The Borough of Merthyr Tydfil, and the District of Rhymney Valley wards Nos. 5 and 14 to 20.

1997–2010: The County Borough of Merthyr Tydfil, and the Caerphilly County Borough wards of Abertysswg, Darren Valley, Moriah, New Tredegar, Pontlottyn, Tir-Phil, and Twyn Carno.

2010–2024: The Merthyr Tydfil County Borough electoral divisions of Bedlinog, Cyfarthfa, Dowlais, Gurnos, Merthyr Vale, Park, Penydarren, Plymouth, Town, Treharris, and Vaynor, and the Caerphilly County Borough electoral divisions of Darran Valley, Moriah, New Tredegar, Pontlottyn, and Twyn Carno.

As its name suggests, the main towns were Merthyr Tydfil and Rhymney. Aberfan was also located in the constituency. The seat was bordered by the constituencies of Blaenau Gwent, Brecon and Radnorshire, Caerphilly, Cynon Valley, and Islwyn.

History
The constituency was created for the 1983 general election. Prior to this, Merthyr Tydfil had been in its own eponymous constituency, and Rhymney was in the seat of Ebbw Vale (at the time Michael Foot's constituency), which was abolished at that election.

Elections in the 2010s
Of the 80 rejected ballots:
 * 22 were either unmarked or it was uncertain who the vote was for.
 * 57 voted for more than one candidate.
 * 1 had writing or mark by which the voter could be identified.

Of the 95 rejected ballots:
 * 49 were either unmarked or it was uncertain who the vote was for.
 * 46 voted for more than one candidate.

Of the 71 rejected ballots:
 * 41 were either unmarked or it was uncertain who the vote was for.
 * 30 voted for more than one candidate.

Of the 83 rejected ballots:
 * 23 voted for more than one candidate.
 * 4 had writing or mark by which the voter could be identified.
 * 56 had want of official mark.