Marine Le Pen says she has called to congratulate French presidential rival Emmanuel Macron after exit estimates projected a heavy defeat for the far-right candidate.
Initial estimates from CNN's affiliate BFMTV-Elabe suggest Macron is expected to take 65.9% of the vote, while Le Pen is expected to gain 34.1%.
Security was tight across France as voters cast their ballots on Sunday. with the the last polling stations closing at 8 p.m. local time (2 p.m. ET).
Macron cast his ballot in Le Touquet, northern France, while Le Pen voted in Henin-Beaumont.
In the first round two weeks ago, voters rejected representatives of all the traditional mainstream political parties in France. Macron and Le Pen topped an 11-strong field, taking 24% and 21% of the vote respectively.
Eleventh hour hack
The two-round election, which has played out like something of a soap opera, was hit with another scandal at the eleventh hour, when Macron's campaign announced it had been the target of a "massive and coordinated" hacking operation.
Around 14.5 gigabytes of emails, personal and business documents were posted to the text-sharing site Pastebin just hours before the campaign period came to a close Friday night.
Macron's party said the hackers had mixed fake documents with authentic ones "to create confusion and misinformation." It is not clear who was behind the attack.
Whoever wins will look forward to elections to the national assembly in June. Macron, whose party En Marche! is less than a year old, is starting from scratch. If he does not persuade enough voters to back his candidates, he will have to strike deals with other parties in order to push through his legislative agenda.
Le Pen's Front National has only two members out of 577 in the national assembly.
Macron, a former investment banker, who also served as economy minister under President Francois Hollande, had struggled to connect with voters in the rural and de-industrialized areas of the country.
Le Pen has also battled to broaden her appeal. At the end of last month she announced that she had temporarily stepped down from her position as leader of the Front National.