Six candidates will be standing in the Brecon and Radnorshire by-election.
The election was triggered after Tory MP Chris Davies was unseated by a petition that followed his conviction for a false expenses claim.
He has been reselected. Candidates from Labour, the Liberal Democrats, the Brexit Party, UKIP, and the official Monster Raving Loony Party have also been nominated. Plaid Cymru and the Greens have decided not to take part.
The poll takes place on 1 August.
Nominated candidates are
- Welsh Conservatives: Chris Davies
- Welsh Labour: Tom Davies
- Welsh Liberal Democrats: Jane Dodds
- Brexit Party: Des Parkinson
- UKIP: Liz Phillips
- The Official Monster Raving Loony Party: Lady Lily The Pink
Applications for postal votes need to be made by 17:00 BST on 17 July. More information can be found on the Powys Council website.