French voters are choosing their next president after an unpredictable campaign that has divided the country.
The second round contest pits centrist Emmanuel Macron, a 39-year-old former investment banker, against the far-right nationalist Marine Le Pen, 48.
The latest figures show voter turnout is sharply down on the past two presidential elections.
The vote is being closely watched across Europe, as the results could affect the future of the EU.
Polling opened at 08:00 local time (06:00 GMT) and the final stations close at 20:00 (18:00 GMT), with early estimates of the result set to be reported immediately after.
More than 50,000 police officers have been deployed to maintain security.
Both candidates have been in the north of France on Sunday, with Mr Macron voting near his home in the seaside resort of Le Touquet, and Ms Le Pen in the working class town of Hénin-Beaumont, a stronghold of…