Ukrainians have begun voting in an election expected to thrust a comedian with no prior political experience into the presidency of a country at war and hungry for change.
At stake is the leadership of a country on the frontline of the West's stand-off with Russia following the 2014 Maidan street protests and the annexation of Crimea.
Surveys make Volodymyr Zelenskiy, who plays a fictitious president in a TV series, the overwhelming favourite to defeat incumbent Petro Poroshenko, whose popularity has been dragged down by patchy efforts to tackle corruption and sliding living standards.
Both men - who traded insults and accusations in a rowdy debate in a soccer stadium in Kiev on Friday - have pledged to keep Ukraine on a pro-Western course.
But a victory for Zelenskiy in Sunday's second-round runoff would nonetheless be a dramatic departure in a country where previous presidential elections since independence were won by experienced politicians including three former prime ministers.
Investors are seeking reassurances that whoever wins will accelerate reforms needed to attract foreign investment and keep the country in an International Monetary Fund programme that has supported Ukraine through war, recession and a currency plunge.
Zelenskiy's unorthodox campaign relied heavily on quirky social media posts and comedy gigs instead of traditional rallies and leaf-letting.
He has also promised to fight corruption, a message that has resonated with Ukrainians who are fed up with politics as usual in a country of 42 million people that remains one of Europe's poorest nearly three decades after winning independence from the Soviet Union.
An opinion poll by the KIIS research firm showed Zelenskiy with 72 per cent of the vote and Poroshenko with 25 per cent. Last week, a different survey put them on 61 per cent and 24 per cent respectively.
Zelenskiy's rise comes at a time of a political upheaval in many parts of the world, from Brexit to the election of US President Donald Trump, the 5-Star Movement in Italy - also inspired by a comedian - and the rise of the far right there, in France and in Spain.
Poroshenko was elected amid high hopes for change after the Maidan protests. He inherited a difficult situation in 2014 and implemented many reforms but has not convinced voters that he is serious about tackling corruption.
Zelenskiy remains something of an unknown quantity and faces scrutiny over his ties to a powerful oligarch who would like to see Poroshenko out of power.
Poroshenko has sought to portray his opponent as a buffoonish populist whose incompetence would leave Ukraine vulnerable to Russia.
Ukrainian troops have battled Kremlin-backed separatist fighters since 2014 in a conflict in the eastern Donbass region that has killed 13,000 people despite a notional ceasefire.
Australian Associated Press