French polling agency projections show President Emmanuel Macron and far-right rival Marine Le Pen leading in the first round of the presidential election.
If borne out by official results, the two will advance to a presidential run-off on April 24 with strong echoes of their last face-off in the 2017 election.
But the second round is likely to be tight.
The election’s result will impact Europe’s direction as it tried to contain Russia and the havoc wreaked by Russian President Vladimir Putin’s war on Ukraine.
Official results are expected later on Sunday night.
Pollsters suggest that just a few percentage points could separate the familiar foes in the second-round vote.
That nail-biting scenario sets up a run-off campaign likely to be far more confrontational and volatile than during round one, which was largely overshadowed by the war in Ukraine.
It might also not be cheered in the Kremlin: Mr Macron has strongly backed European Union sanctions on Russia, while Ms Le Pen has worried publicly about their impact on French living standards.
Ms Le Pen gave a little wink on Sunday as she dropped the blue envelope containing her choice into a ballot box in the northern town of Henin-Beaumont.
Afterward, she said “given the situation in the country and in the world”, Sunday’s election outcome could determine “not only the next five years, but probably the next 50 years” in France.
In the 27-member EU, only France has a nuclear arsenal and a UN Security Council veto. As Mr Putin keeps up his military’s assault on Ukraine, French power is helping to shape the European response.
Mr Macron is the only leading French presidential candidate who fully supports the Nato military alliance.
Mr Macron and his wife, Brigitte, voted together in the seaside resort of Le Touquet, making their choices in voting booths covered by curtains of blue, white and red — the colours of the French flag.
Mr Macron for months looked like a certain to become France’s first president in 20 years to win a second term.
But National Rally leader Ms Le Pen ate into his polling lead in the campaign’s closing stages, as the pain of rising fuel, food and energy prices became a dominant election theme for many low-income households.
Mr Macron’s win over Ms Le Pen in 2017 to become France’s youngest modern president was seen as a victory against populist, nationalist politics, coming in the wake of Donald Trump’s election to the White House and Britain’s vote to leave the European Union, both in 2016.
To beat Ms Le Pen in a run-off, the 44-year-old president will need to pick apart her years-long rebranding effort to make herself seem more pragmatic and less extreme, a makeover that has including showing off her love of cats.
Mr Macron has accused Ms Le Pen of pushing an extremist manifesto of racist and ruinous policies. Ms Le Pen wants to ban Muslim headscarves in French streets and halal and kosher butchers, and drastically reduce immigration from outside Europe.
