This is a list of by-elections to the Senedd (Welsh Parliament; ; formerly known as the National Assembly for Wales). Where seats changed political party at the by-election, the result is highlighted. Assembly termBy-election Date Incumbent Party Winner Party Cause Retained at next election2021–2026Caerphilly23 October 2025Hefin David Labour Lindsay Whittle Plaid CymruDeath (suicide) N/A2016–2021Alyn and Deeside6 February 2018Carl Sargeant Labour Jack Sargeant Death (suicide)Yes2011–2016Ynys Môn1 August 2013Ieuan Wyn Jones Rhun ap Iorwerth Resignation to lead the Menai Science ParkYes2003–2007Blaenau Gwent29 June 2006Peter Law LabourTrish Law Death (brain tumour)Yes1999–2003Swansea East27 September 2001Val Feld LabourValerie Lloyd LabourDeath (cancer)Yes
See also List of by-elections to the Scottish Parliament Regional member changes to the Senedd
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