Unions are reportedly already planning a protest on Monday, regardless of whether Le Pen or Macron wins.
Polling agency projections and initial official results are expected as soon as the final stations close at 8pm (6pm GMT).
Yesterday the rest of the world watched as the most unpredictable and important French presidential campaign in recent memory ended with a hacking attack targeting Macron on Friday night, just hours before the country went into media blackout.
France's government cybersecurity agency, ANSSI, is investigating the hack, which Macron's team says was aimed at destabilising the vote.
The fate of the European Union may hang in the balance as France's 47 million voters decide whether to risk handing the presidency to Le Pen.
The far right candidate has made no secret of her dream to quit the EU and its common currency. Macron on-the-other-hand is an unabashed pro-European who wants to strengthen the bloc.
Global financial markets and France's neighbors are watching carefully. A 'Frexit' would be far more devastating than Britain's departure, since France is the second-biggest economy to use the euro.
The country is also a central pillar of the EU and its mission of keeping post-war peace via trade and open borders.
The vote will help gauge the strength of global populism after the UK opted out of the EU in June last year and Donald Trump won the U.S presidential election.
In France, it is a test of whether voters are ready to overlook the racist and anti-Semitic past of Le Pen's National Front party.
Le Pen has broadened the party's appeal by tapping into, and fueling, anger at globalisation and fears associated with immigration and Islamic extremism.
Macron has argued that France must rethink its labor laws to better compete globally and appealed for unity and tolerance. Le Pen has called his policies naive.
Either candidate would lead France into uncharted territory, since neither comes from the mainstream parties that dominate parliament or have experience running the country.
The winner will have to try to build a parliamentary majority in elections next month to make major changes.
Fears of outside meddling hung over the race after France's election campaign commission said yesterday that 'a significant amount of data', along with some fake information, was leaked on social networks following the hacking attack on Macron.
The leaked documents appeared largely mundane, and the perpetrators remain unknown. It's unclear whether the document dump will dent the large polling lead Macron held over Le Pen going into the vote.
The commission urged French media and citizens not to pay attention to the leaked documents. French electoral laws impose a weekend news blackout on any campaigning and media coverage seen as swaying the election meaning Le Pen's campaign could not formally respond due to the blackout.
The Macron team asked the campaign oversight commission to bring in cybersecurity agency ANSSI to study the hack, according to a government official who spoke to The Associated Press on the condition of anonymity.
ANSSI can only be called in to investigate cyberattacks that are 'massive and sophisticated' - and the Macron hack appears to fit the bill, the official said.
The documents leaked Friday were widely circulated on far-right sites based in the U.S. Experts dissecting the data said they spotted some Russian names in the dump.
From depressed northern France to the streets of Paris, some voters were just looking forward to the end of the vitriolic campaign.
In Henin-Beaumont in northern France, where Le Pen will cast her ballot, Thomas Delannoy, 28, said the campaign 'looks like reality TV.'
The construction painter called the electoral process 'laughable,' saying that neither candidate had a platform with which he could identify.
Many voters expressed similar frustration, and a big question remaining Sunday was how many of them would bother to vote.
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