; ) is a six-member constituency of the Senedd (Welsh Parliament; ) used in the 2026 Senedd election. It covers areas in the south-east of Wales, particularly parts of Cardiff, Rhondda Cynon Taf and the Vale of Glamorgan.
It was proposed following the 2026 review of Senedd constituencies, and is a pairing of the two UK Parliament constituencies of Cardiff West and Cardiff South and Penarth. It has a Welsh-only name.
Boundaries A Senedd constituency comprising the boundaries of the UK Parliament constituencies of Cardiff West and Cardiff South and Penarth, 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 Cardiff West, South and Penarth in September 2024. The pairing was then switched from Cardiff West to Cardiff East and renamed to Cardiff South-east Penarth, and its Welsh name being in December proposals, despite most other constituencies using Welsh-only names. It was later given the Welsh-only name and its boundaries were reverted back to using Cardiff West rather than Cardiff East in the commission's final recommendations in March 2025. When announcing their candidates, Reform UK used "Cardiff South-west Penarth" instead, based on the English names for the pair of UK Parliament constituencies that form it.
It encompasses parts of the principal areas (counties/county boroughs) of Cardiff, Rhondda Cynon Taf and the Vale of Glamorgan in South Wales. The constituency was established in 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. Members of the Senedd Term Election Distribution MS MS MS MS MS MS 7th 2026 1 3 1 1 Anna Brychan(PC) Kiera Marshall(PC) Joseph Martin(Ref) Anthony Slaughter(Grn) Leticia Gonzalez(PC) Huw Thomas(Lab)
Elections Elections in the 2020s
2021 notional result Party Vote % Seats Labour 35,502 48.2 4 Conservative 14,210 19.3 1 Plaid Cymru 10,913 14.8 1 Propel 3,947 5.4 0 Liberal Democrats 3,083 4.2 0 Green 2,897 3.9 0 Abolish 1,466 2.0 0 Reform UK 490 0.7 0 UKIP 389 0.5 0 Independent 355 0.4 0 Freedom Alliance 237 0.3 0 Gwlad 110 0.1 0 Socialist (GB) 18 0.0 0
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