Why is it important?
France is the eurozone's second-biggest economy as well as a global military and diplomatic heavyweight, with veto power as a permanent member of the UN Security Council.
The second round will come down to a battle between the pro-European, pro-globalisation vision of Macron and Le Pen's hostility to the EU and NATO.
If Le Pen wins, it will further shake up the West's liberal post-war order, already rattled by Britain's vote to leave the EU and Donald Trump's election to the White House.
How is the president elected?
The president is elected directly by the people in a vote of one or two rounds. With neither candidate obtaining an absolute majority in the first round, a run-off will be held two weeks later. Every presidential election since 1965 has gone to a second round.
Who ran in the first round?
Eleven candidates spanning the spectrum from Trotskyist left to far-right took part in Sunday's first-round vote.
The main candidates were Macron, 39, Le Pen, 48, conservative Francois Fillon, 63, and hard-left firebrand Jean-Luc Melenchon, 65.
The other candidates were: Socialist nominee Benoit Hamon, 49; Philippe Poutou, a 50-year-old Ford factory worker; pro-sovereignty candidates Nicolas Dupont-Aignan, 56, Francois Asselineau, 59 and Jacques Cheminade, 75; Trotskyist economy teacher Nathalie Arthaud, 47, and Jean Lassalle, a 61-year-old MP and former shepherd.
How does the election work?
A total of 46.87 million voters were registered to vote. The country's 66,546 polling stations opened at 8:00 am (0600 GMT) and most closed at 7:00 pm, although they remained open an hour longer in Paris and other big cities.
Turnout was around 69.4 percent at 1500 GMT, three hours before the final polling stations closed, slightly down on the same point in the 2012 election.
The election is the first in the history of France's 59-year-old Fifth Republic to take place under a state of emergency.
More than 50,000 police backed by 7,000 soldiers from the Sentinelle (Sentry) anti-terror operation were on patrol.
What happens next?
Voters are called back to the polls for the May 7 runoff and the next president will be sworn in by May 14 at the latest. The new president will take over from Socialist Francois Hollande.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)