Monmouthshire () is a constituency of the House of Commons in the UK Parliament, and was first contested at the 2024 general election, following the 2023 review of Westminster constituencies. Its current MP is Catherine Fookes, a member of the Labour Party.
It previously existed as a county constituency of the House of Commons of the Parliament of England from 1536 until 1707, of the Parliament of Great Britain from 1707 to 1801, and of the Parliament of the United Kingdom from 1801 to 1885. It elected two Members of Parliament (MPs).
In 1885 the Monmouthshire constituency was divided to create North Monmouthshire, South Monmouthshire and West Monmouthshire.
Monmouthshire was given representation in the Parliament of England by the Laws in Wales Acts 1535 and 1542. This was later a key point in the long-standing argument about whether the county was or was not part of Wales.
Until the Great Reform Act of 1832, the historic Monmouthshire county constituency covered almost the whole of the county of Monmouth, but not the county town of Monmouth, which was a separate borough constituency. In 1832 this was expanded into the Monmouth Boroughs, taking in more towns to give it more electors.
The Redistribution of Seats Act 1885 split the county constituency into three, North, South, and West Monmouthshire, and then the Representation of the People Act 1918 abolished these, with most of the county joining a new seat called Monmouth. This included the towns of Chepstow, Monmouth, and Abergavenny.
The Monmouthshire constituency was re-established as part of the 2023 review for the 2024 general election under the June 2023 final proposals of the Boundary Commission for Wales. The boundaries were defined as being coterminous with the unitary authority of the County of Monmouthshire, so it does not now include those parts of the county in the area of the Newport City Council.
Monmouth and Newport East prior to 2024
Somerset was appointed Comptroller of the Household, triggering a by-election.
Somerset resigned, triggering a by-election.
Somerset resigned by accepting the office of Steward of the Manor of Hempholme, triggering a by-election.
Somerset's death caused a by-election.
Somerset was appointed Chancellor of the Duchy of Lancaster, triggering a by-election.
Williams resigned by accepting the office of Steward of the Chiltern Hundreds, triggering a by-election