Voters in France are heading to the polls to decide whether to give centrist Emmanuel Macron five more years as president or replace him with far-right candidate Marine Le Pen.
After a divisive election campaign, Ms Le Pen faces an uphill battle with her 44-year-old opponent polling ahead.
In order to win they both need to attract voters who backed other candidates in the first round.
But these are two polarising figures in France and abstention is a key factor.
Mr Macron’s detractors call him arrogant and a president of the rich, while the far-right leader has been accused of having ties to Russian President Vladimir Putin.
Polls opened in the run-off vote at 08:00 (06:00 GMT) and 48.7 million people were eligible to take part. First projections of who has won will come at 20:00.
Mr Macron rose to power on a whirlwind promise of change, but many complain they are yet to see it. His presidency has been buffeted by protests, the Covid pandemic and now the rising cost of living.
Marine Le Pen, meanwhile, has learned from the mistakes she made when she was resoundingly beaten by the same opponent in the second round in 2017. This is her third tilt at the presidency and if she fails it could be her last.
The great unknown in this election is how many voters will refuse to back either candidate, whether by casting a blank ballot or not turning out at all. Much of France is on holiday and turnout could be historically low.
The campaign has been short but the choice for voters is clear, between a pro-European sitting president and a nationalist candidate who seeks to ban the headscarf and restrict immigration.
Whatever the result, Mr Macron will address voters on Sunday evening from a stage at the foot of the Eiffel Tower.
Unemployment may be down and purchasing power may be higher than in 2017, but many voters on the left are disillusioned with the sitting president for cutting housing aid to millions of low earners and abolishing a wealth tax that targeted millionaires.
When Emmanuel Macron swept to power, it was on the promise of change. But a remark you hear everywhere is that nothing has changed at all.
If the opinion polls are accurate and he does win, he will not face an easy second term.