It was proposed following the 2026 review of Senedd constituencies, and will be a pairing of the two UK Parliament constituencies of Monmouthshire and Torfaen. It is to have a Welsh-only name.
A Senedd constituency comprising the boundaries of the UK Parliament constituencies of Monmouthshire and Torfaen, has been proposed by the Democracy and Boundary Commission Cymru for the 2026 election to the Senedd (Welsh Parliament; ). It was initially proposed using the English name Monmouthshire and Torfaen in September 2024, but was renamed to in December proposals with most constituencies using Welsh-only names. It was then given the Welsh-only name and its boundaries were confirmed in the commission's final recommendations in March 2025. When announcing their candidates, Reform UK used "Monmouthshire, Torfaen" instead, using the English names for the pair of UK Parliament constituencies that form it.
It encompasses the entire principal areas (counties/county boroughs) of Monmouthshire and Torfaen in South Wales. The constituency is to be established by 2026, following the passing of the Senedd Cymru (Members and Elections) Act 2024. The act legislates electoral reform of the Senedd to create 16 larger "super constituencies", pairing the 32 UK Parliament constituencies in Wales, and using a new fully proportional voting system, with each constituency electing six Members of the Senedd (MSs) rather than one previously.