Ukrainians are heading to the polls in a run-off election to pick the country’s next president.
Voters face a stark choice between tycoon Petro Poroshenko, the incumbent president, and television comedian Volodymyr Zelensky, new to politics.
The TV celebrity is favourite in the polls, having dominated the first round of voting three weeks ago when 39 candidates were on the ticket.
Polling stations opened 08:00 (05:00 GMT) and will close 12 hours later.
A court in the capital, Kiev, has rejected a lawsuit calling for Mr Zelensky to be barred from standing.
A man had complained that the distribution of free tickets for a presidential debate by Volodymyr Zelensky’s candidacy amounted to bribery.