Ukrainian comedian Volodymyr Zelensky has won a landslide victory in the country’s presidential election, exit polls suggest.
The polls give the political newcomer, who dominated the first round of voting three weeks ago, more than 70% support.
Mr Zelensky, 41, challenged incumbent president Petro Poroshenko who has admitted defeat.
The apparent result is being seen as a huge blow to Mr Poroshenko and a rejection of Ukraine’s establishment.
“I will never let you down,” Mr Zelensky told celebrating supporters on Sunday.
“I’m not yet officially the president,” he added. “But as a citizen of Ukraine I can say to all countries in the post-Soviet Union: Look at us. Anything is possible!”
If polls are correct, he will be elected for a five-year term.
Ukraine’s president holds significant powers over the security, defence and foreign policy of the country.
Humiliation for Poroshenko
Analysis by Jonah Fisher, BBC News, Kiev
Ukraine’s choice was between an experienced politician with five years as president on his CV and a comedian wielding little more than a blank sheet of paper. That so many people have opted for Volodymyr Zelensky is a humiliation for Petro Poroshenko.
Thirty-seven candidates were removed from the ballot paper from the first round and yet the president only picked up about 9% more votes this time. Mr Zelensky gained almost 45 percent.
This feels like a massive protest vote and for now Mr Zelensky and his campaign team are celebrating.
It’s hard to see the feeling lasting long. The hard work will come when they have to start fleshing out what are at the moment vague policies.
It’s one thing to have bold ideas but quite another to implement them.
Polls gave Mr Poroshenko, who has been in power since 2014, 25% of the vote.
“The outcome of the election leaves us with uncertainty [and] unpredictability,” he said after exit polls were released.
He added: “I will leave office but I want to firmly stress – I will not quit politics.”
The billionaire was elected after an uprising overthrew the country’s previous pro-Russian government.
Russian forces annexed Ukraine’s Crimea peninsula in March 2014 – a move condemned internationally. Since then, Ukrainian forces have been fighting Russian-backed separatists and volunteers in the east.
In a tweet, Mr Poroshenko said “a new inexperienced Ukrainian president… could be quickly returned to Russia’s orbit of influence”.
But Russia’s foreign ministry said Ukrainian voters had expressed their desire for political change.
“The new leadership now must understand and realise the hopes of its electors,” deputy foreign minister Grigory Karasin told the RIA Novosti news agency. “This of course applies to domestic as well as foreign affairs.”
Meanwhile, Mr Zelensky told a news conference on Sunday that he would “reboot” peace talks with the Russian separatists.
Who is Volodymyr Zelensky?
Mr Zelensky is best known for starring in a political satirical drama called Servant of the People in which his character accidentally becomes Ukrainian president.
He ran under a political party with the same name as his show.
With no previous political experience, his campaign focused on his difference to the other candidates rather than on any concrete policy ideas.
Despite this, he won the first round with more than 30% of the vote – almost double what Mr Poroshenko got when he finished in second place with 15.95%.
What do voters think of him?
Analysts believe Mr Zelensky’s informal style and vow to clean-up Ukrainian politics resonated with voters who are disillusioned with the country’s path under Mr Poroshenko.
Eschewing traditional campaign tactics, Mr Zelensky channelled his on-screen persona by promising to stamp out corruption and loosen the grip of oligarchs on Ukraine.
Experts say his supporters, frustrated with establishment politicians and cronyism, have been energised by his charisma and anti-corruption message.
His critics, meanwhile, are sceptical about his credentials, with many expressing concern over his close links to the billionaire oligarch Ihor Kolomoyskyi.
They have expressed doubts that he will be able to take on the country’s influential oligarchs and stand up to Russian President Vladimir Putin.