Plaid Cymru leader Rhun ap Iorwerth says he is ready to lead the Welsh government after a stunning election victory left his party the largest group in the Senedd.
Addressing his fellow MSs and supporters in Cardiff Bay, ap Iorwerth said it was an "immense honour" to be able to represent the whole of Wales.
He told reporters he is seeking to run a minority government, meaning Plaid will try to govern alone without a coalition. He said he had spoken to other party leaders but did not say who.
Meanwhile Labour has appointed Ken Skates interim Welsh party leader, following Eluned Morgan's resignation after losing her seat on Friday.
Thursdays historic vote saw Plaid win 43 seats and Reform UK come second with 34, pushing Labour into third with just nine seats in the expanded 96-member Senedd - ending a century-long run of election success in Wales.
In his speech on the steps of the Senedd on Saturday, ap Iorwerth said: "Throughout our nation people have put their faith in Plaid Cymru in numbers never seen before."
"And we will do everything we can to repay the faith that people have put in us because we have a clear determination to make a difference on the things that matter to people's lives and that resonated to people on all corners of our country," he said.
Ap Iorweth said he was "inviting everyone to join us in an alliance, to pursue this mission on behalf of Wales".
"We say we will always act with a determination, the ambition, and the humility needed to make Wales the best it possibly can be, we will do this every day for Wales," he said.
"It is a new beginning and I have no doubt that, when we speak with a national voice that is as determined as we have seen in this election, no UK government, no UK minister, now or in the future, can cast Wales aside or turn a blind eye to our needs and our aspirations as a nation."
Plaid fell short of a majority in Cardiff Bay, but with 43 seats has a better chance than anyone of forming a government with the help of at least some opposition politicians.
The Senedd will need to confirm who will lead the Welsh government in a vote, which could happen as early as Tuesday.
BBC Wales understands that Labour is likely to abstain the vote, which would ease the way for ap Iorwerth to be confirmed as first minister.
In government he would likely require the support of opposition Members of the Senedd (MSs) to get important votes through parliament.
No party has formally ruled out working with them, unlike Reform UK which Plaid, Labour, the Lib Dems and Greens have said they would refuse to assist.
Plaid is pro-independence but tried to put the issue in the distance during the campaign.
It has ruled out pushing for a referendum on separating Wales from the rest of the UK in the first term of a government, but has said a commission would begin to build the case for an independent Wales.
The decision to give Skates, Senedd member for Fflint Wrecsam, the temporary Labour leadership role followed meetings of the party's national executive and Senedd group on Saturday.
Labour said the MS, who has held posts in government including transport and the economy portfolios, will remain interim leader until a timetable is set out for a full leadership election.
Skates paid tribute to Morgan, saying: "We are a party with an incredible history of serving Wales and her people, and we have so much more to give."
Labour has won every general election since 1922 in Wales and, until this week, every Cardiff Bay election since the Senedd's predecessor the National Assembly was established in 1999.
It had been in charge of the Welsh government for 27 years.
Plaid had appealed to voters to back them to stop Reform - a strategy cited by many in Labour as behind the party's success, and Labour's failure.
Morgan, who took over Welsh Labour in 2024 after a period of turmoil in the party over her predecessor, is the first leader of a government in the UK to lose their seat while in office.
Morgan said she would resign as Welsh Labour at her election count in Llandysul on Friday, and said she took "full responsibility" for the result while also calling for the UK Labour government to "change course".
"It is clear that results across the whole of the United Kingdom have demonstrated deep frustration with the Labour Party. We need to go back to being the party of the working class," she said.
She also congratulated Plaid Cymru on "their momentous success".
Morgan was one of two sitting Labours minister to lose her seat, with the other being Jack Sargeant, minister for culture.
Many of the rest of their senior colleagues are standing down at this Senedd election.
Some in the party have blamed the UK government for Labour's loss in Wales, including former minister Mick Antoniw, who has called for Sir Keir Starmer to resign.
Labour sources told BBC Wales throughout the campaign that the prime minister came up negatively with voters on doorsteps.
Sources said that a "grudging" acknowledgement that he had handled the UK's response to the Iran war well had been soured by the Lord Mandelson saga.
But Alex Barros Curtis, Cardiff West Labour MP, suggested blame may also lay with the Welsh government.
He said after 27 years "maybe the pendulum swings away from you. I don't deny that Westminster would come up a little bit, but I don't think it's anchored in Keir Starmer."
Reform's Welsh leader Dan Thomas will become an MS after he topped the poll in Casnewydd Islwyn - the seat that covers Newport and the valley between the city and Blackwood.
Appointed only in February by UK leader Nigel Farage, Thomas had suggested the party could win a majority.
The party largely had a standing start, having won no MSs at the last election in 2021. Two Tories politicians had joined the party in the last Senedd term.
Reform finished second with 34 MSs.
Thomas said: "In just five years, Reform has gone from winning 1% of the vote in the Senedd elections to being the main contender for government, smashing Labour in the process.
"It has taken Plaid Cymru decades to come anywhere near to the same. The momentum is with Reform, because we are the people's army."
Reform's Llyr Powell lost last year's Senedd by-election in Caerphilly, but will be a Reform MS after he was successful in the new constituency of Blaenau Gwent Caerfilli Rhymni.
Powell acknowledged expectations had been high for Reform, but said the campaign had been about "building from the ground up".
"It's like building an aeroplane mid-flight," he said.
"People were asking where the candidates were, where the manifesto was, where the leader was. But we've worked hard, people have come out for us, and they supported what we were saying."
He added that Reform's presence in the Senedd would now be about "building momentum" after a strong electoral showing.
Welsh Conservative leader Darren Millar returned to the Senedd with a group of seven Senedd members.
Polls at various points during the campaign had suggested the party could face a wipe-out.
The Greens gained their first seats to the Senedd, winning one each in Caerdydd Penarth and Caerdydd Fynnon Taf.
The leader of the Welsh Liberal Democrats Jane Dodds returned to the Senedd, but like in 2021 she remains the Senedd's only Liberal Democrat.
Voters have elected a new larger Senedd for the first time, with the number of seats increasing from 60 to 96, elected in 16 large constituencies of six seats each.
But a new election system has seen smaller parties - including the UK's historic parties of government, Labour and the Conservatives - squeezed into single figures.
The gender balance in the new Senedd has slightly improved after the election.
Female members now make up 46% of the 2026 intake, compared to 43% in the old Senedd. There are now 52 male MSs and 44 female.
There are only two constituencies - Pontypridd Cynon Merthyr and Ceredigion Penfro - where female MSs outnumber male ones.
Only 29 MSs have returned from the last term - 70% of the new parliament are new.
Presiding officer Elin Jones is now the longest-running member of the Senedd, having been elected in the first assembly election for Plaid Cymru in 1999.
She is expected to quit the role, which sees her chairing meetings of the parliament, when it meets for the first time after the election.
Additional reporting by Mark Palmer, Steve Duffy and Shelley Phelps
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