Update - 10.40pm: The President of Ireland Michael D. Higgins has written to President-elect Emmanuel Macron to convey his best wishes.
In his message, President Higgins said the French President-elect's many references to the need for renewal of European purpose, based on European values and a commitment that his Presidency will engage not only with French but European and global matters, will be welcomed by all those seeking a positive discourse on contemporary issues, which are perceived as threats by many.
Update - 10.20pm: The Taoiseach Enda Kenny has congratulated Emmanuel Macron on his victory, calling him "a leader with a positive ambition for Europe".
Mr Kenny said:" I want to extend my congratulations, and that of the Irish Government, to Emmanuel Macron on his victory in the French presidential election.
"I am delighted that a leader with a positive ambition for Europe has won this election decisively and will join us with a strong mandate in the European Council.
"Ireland and France share close bonds; from General Humbert in my own county of Mayo in 1798 to the joyous scenes all over France at the European Championships last Summer. Our shared history has been both deep and varied. The future also holds promise as both countries work towards a European Union of prosperity and equality for all our citizens.
"There's lots of work ahead for all of us in Europe, in a challenging environment, not least on Brexit. I am confident that under Emmanuel Macron's leadership, France will continue to play an important role in the EU.
"This outstanding result is a strong signal of confidence in the future of the European Union in which France will play a significant part in the time ahead."
At a victory rally, Mr Macron said that France is facing an "immense task" to rebuild European unity, fix the economy and ensure security against extremist threats.
Speaking to thousands of supporters from the Louvre Museum's courtyard, he said that Europe and the world are "watching us" and "waiting for us to defend the spirit of the Enlightenment, threatened in so many places".
Mr Macron, who has never held public office and just founded his political movement a year ago, said "everyone said it was impossible. But they didn't know France".
He also promised to work to unify France after a bruising presidential campaign and serve the country "with love".
His wife Brigitte then came up on stage with him, and she kissed his hand and waved to the crowd.
British Prime Minister Theresa May has "warmly" congratulated France's new President-elect.
She says France is "one of the UK's closest allies" and she "looks forward to working with the new President on a wide range of shared priorities."
Update - 9.55pm: In a tweet, US President Donald Trump said: "Congratulations to Emmanuel Macron on his big win today as the next President of France. I look very much forward to working with him."
Congratulations to Emmanuel Macron on his big win today as the next President of France. I look very much forward to working with him!— Donald J. Trump (@realDonaldTrump) May 7, 2017
A White House statement cited Mr Macron and the French people for "their successful presidential election" and said the United States looks forward to "continuing our close relationship with the French government".
MEP, Brian Hayes, said Mr Macron's election is a victory for peace and prosperity in the EU.
The Fine Gael Dublin MEP welcomed his "convincing victory".
He said: "It is a beacon of hope against the narrow nationalism of Trump and Brexit. It's a beacon of hope for a new Europe in the post-Brexit world.
"The politics of the French populists have been roundly defeated as they have in other EU Member States. This year, 2017, is a new year of hope for Europe. In Austria and in the Netherlands the populists have shown that they are now on the retreat - they have no solutions. They have nothing to offer but fear and recrimination.
"The election of Macron must focus minds within Europe about what we need to do. We need to provide hope and prosperity to a generation of Europeans who want the EU to do much more. The election of Macron brings with it a chance for a fresh start for the EU. It's an election for peace and prosperity - an election for the future of Europe.
"The renewal of France is inextricably linked to the renewal of Europe. We need to work together both as an EU Parliament and as a new French presidency."
Update - 8.15pm: French president-elect Emmanuel Macron says a "new page of our history" has opened, after he defeated far-right populist Marine Le Pen.
Voters delivered a resounding victory for the pro-European former investment banker, strengthening France's place as a central pillar of the EU, and he immediately vowed to "defend France and Europe".
He acknowledged divisions in society which drove people to "vote to the extreme", and said he will work for all of France.
A crowd of Macron supporters roared with delight, jubilantly waving red, white and blue tricolour flags at a victory party outside the Louvre Museum in Paris.
Ms Le Pen said she had called the 39-year-old to concede defeat after voters rejected her "French-first" nationalism by a large margin.
After conceding defeat, she immediately turned her focus to France's upcoming legislative elections in June, where Mr Macron will need a working majority to govern effectively.
"I call on all patriots to join us," she said. "France will need you more than ever in the months ahead."
Earlier: French far-right presidential candidate Marine Le Pen says she has called Emmanuel Macron to congratulate him on his victory.
Mr Macron's supporters have been pouring into the courtyard outside the Louvre museum in Paris, where he plans to celebrate.
Mr Macron looks set to become France's next president after exit polls gave him a strong lead over the far-right populist leader.
Polling agencies project the 39-year-old political novice has won 65% of the vote, with Ms Le Pen trailing on 35%.
If confirmed, Ms Le Pen's showing would still be stronger than her National Front party has seen in its 45-year history.
Mr Macron would become the youngest French president ever, putting him at the helm of one of the world's biggest economies.
But Ms Le Pen's projected showing, unusually low turnout and the record number of blank ballots are an indication of the headwinds facing Mr Macron, a former economy minister who started his own political movement only a year ago.
Ms Le Pen said she would call for a new political force as legislative elections loom in June.
She also hinted her party may rename itself from the National Front, which has been dogged by allegations of racism and anti-Semitism since it was founded by her father.
French Prime Minister Bernard Cazeneuve said the vote "testifies to the lucidity of the voters who rejected the deadly project of the extreme right".
He added it shows voters have embraced the European Union.
European Council president Donald Tusk said on Twitter: "Congratulations to French people for choosing liberty, equality and fraternity over tyranny of fake news."
Congratulations @EmmanuelMacron. Congratulations to French people for choosing Liberty, Equality and Fraternity over tyranny of fake news.— Donald Tusk (@eucopresident) May 7, 2017
A Macron victory marks the third time in six months - following elections in Austria and Holland - that European voters have shot down far-right populists who want to restore borders across Europe.
Victory for Mr Macron, who had championed European unity, could also strengthen the EU's hand in its complex divorce proceedings with Britain.
Fianna Fáil Leader Micheál Martin has congratulated Mr Macron on his victory, and said he is looking forward to working with him in the future on issues of mutual concern to both Ireland and France.
Mr Martin said: "President-Elect Macron's victory is not only a victory for him, and his movement, but also a victory for the values that Ireland and France share: openness, tolerance and reason.
"His message of inclusion, diversity and respect, allied to his progressive radical economic platform saw him secure victory in an election that caught the imagination of people right across Europe.
"For too long, the politics of fear and division has been seen to be gaining ground on the continent. Those of us who favour a society that is open-minded, progressive and global in its outlook will look at today's result with optimism.
"The European Union faces many challenges in the years ahead. I am heartened that in this election, and in recent elections in the Netherlands and Austria, the progressive centre has held.
"Of course, there are issues on which President-Elect Macron and I will disagree, but on the broad issues of Europe's role in the world, defending the civil rights of our citizens, and building an economy that delivers prosperity for all, we are on the same page."
Outgoing president Francois Hollande congratulated Mr Macron and said his victory shows the overwhelming majority of voters rallied behind the European Union and openness to the world.
It was Mr Hollande who first brought Mr Macron into the world of politics, naming the untested ex-banker as economy minister.
But Mr Macron left the position to found his own political movement last year, and has distanced himself from his former mentor.
German Chancellor Angela Merkel's chief of staff Peter Altmaier congratulated Mr Macron with a tweet saying: "Long live France, long live Europe!"
Vive La France! Vive L'Europe!Signal fort pour nos valeurs communs et Le Franco-Allemand!Felicitations à Emmanuel Macron!Bonne présidence!— Peter Altmaier (@peteraltmaier) May 7, 2017
Her chief spokesman Steffen Seibert said it is a victory "for a strong and united Europe".
Félicitations, @EmmanuelMacron. Votre victoire est une victoire pour une Europe forte et unie et pour l'amitié franco-allemande.— Steffen Seibert (@RegSprecher) May 7, 2017
Outside the Louvre, Mr Macron's jubilant supporters sang "We have won, we have won" while waving French flags as they waited for their new president to arrive.
Many expressed their relief that Ms Le Pen had suffered a clear defeat.
Sandra Ledoux, 32, said she is "very happy because Macron is young, innovative and he has a project to make Europe better instead of destroying it like Le Pen wanted".