List of by-elections to the Senedd

This is a list of by-elections to the Senedd (Welsh Parliament; Welsh : Senedd Cymru; formerly known as the National Assembly for Wales).

Where seats changed political party at the by-election, the result is highlighted.

Assembly term	By-election	Date	Incumbent	Party		Winner	Party		Cause	Retained at next election
2021–2026	Caerphilly	23 October 2025	Hefin David		Labour	TBC		TBC	Death (suicide) [1]	N/A
2016–2021	Alyn and Deeside	6 February 2018	Carl Sargeant		Labour	Jack Sargeant		Labour	Death (suicide) [2]	Yes
2011–2016	Ynys Môn	1 August 2013	Ieuan Wyn Jones		Plaid Cymru	Rhun ap Iorwerth		Plaid Cymru	Resignation to lead the Menai Science Park	Yes
2003–2007	Blaenau Gwent	29 June 2006	Peter Law *		Labour	Trish Law		Independent	Death (brain tumour)	Yes
1999–2003	Swansea East	27 September 2001	Val Feld		Labour	Valerie Lloyd		Labour	Death (cancer)	Yes

*Peter Law left the Labour Party and sat as an independent prior to his death. The by-election was won by his widow, but is classed as an independent gain from Labour.

See also

• List of by-elections to the Scottish Parliament
• Regional member changes to the Senedd

References

1. "Caerphilly politician Hefin David found dead at home - inquest". BBC News. 26 August 2025.
2. "Sacked Labour minister Carl Sargeant found dead". BBC News. 7 November 2017. Retrieved 12 July 2021.