Plaid Cymru have suggested a coalition with other parties might be in the offing after Brecon and Radnorshire Conservative MP Chris Davies was ousted by his constituents.
10,005 people signed the petition to remove the MP, more than the 10% needed for a by-election. A total of 5,303 names were needed to trigger a fresh poll.
The bookies have the Liberal Democrats as favourites to win the seat, with the Brexit Party narrowly in second place.
Mr Davies was convicted of a false expenses claim in March.
Plaid Cymru leader Adam Price had previously written to the leaders of pro-Remain parties during and after the EU Elections, calling on them to work together to push for a People’s Vote.
A Plaid Cymru Spokesperson said: “The people of Brecon and Radnorshire have spoken and a by-election will now take place. This will likely be a crucial first test for the incoming Conservative Prime Minister.
“The two-party status quo in Westminster is breaking down. In last month’s European elections many voters broke the habit of a lifetime by choosing to back pro-People’s Vote parties, rather than the Conservatives or Labour.
“Ensuring those of us who want to see a fresh referendum work together, at every possible level, to deliver this aim is crucial. We will explore options for how we can work together, across party lines, to deliver this in the upcoming Brecon and Radnorshire by-election.”