Conservative candidate Nicolas Sarkozy has won the hotly-contested French presidential election.
The final count gave Mr Sarkozy 53.06%, compared with 46.94% for socialist Segolene Royal, with turnout at 85%.
Mr Sarkozy, 52, the son of a Hungarian immigrant, takes over from the 74-year-old Jacques Chirac.
Riot police have fired tear gas at a small group of demonstrators who were protesting in central Paris against Mr Sarkozy's victory.
According to the French news agency AFP, a few hundred stone-throwing rioters charged the police in the Place de la Bastille, where 5,000 supporters of Segolene Royal had earlier gathered to hear the results.
Friendship for US
Mr Sarkozy's supporters have gathered for an open-air concert in the Place de la Concorde, which is expected to continue until the early hours.
In his victory speech, Mr Sarkozy said he would be the president of all the French.
"France has given me everything, and now it is my turn to give back to France what France has given me," he said.
He said the US could count on France's friendship, but urged Washington to take a lead in the fight against climate change.
He also said he believed deeply in European integration, but appealed to France's partners to understand the importance of social protection.
"[Voters] have chosen to break with the habits and the ideals of the past so I will rehabilitate work, authority, morality, respect, merit!" he said.
After he finished speaking at his party headquarters, jubilant supporters sang a rousing rendition of the French national anthem.
Ms Royal is the first woman ever to have made it to the second round of a French presidential election.
Conceding defeat - the third in a row for France's Socialist Party - she thanked 17m French people for their votes, saying she could measure their sadness and their pain.
"I gave it all my energy, and will continue," she told supporters. "Something has risen up that will not stop."
She expressed the hope that "the next president of the Republic" would accomplish his mission at the service of all the French people.
Mr Sarkozy has promised to try to reform France to face the challenges of the 21st century, with putting the nation back to work at the top of his agenda.
He has pledged to bring unemployment down from 8.3% to below 5% by 2012.
He is also expected to bring forward policies to cut taxes and keep trains running during strikes, in the first 100 days after he takes office on 16 May.
But the BBC's Caroline Wyatt in Paris says he will have to work hard to unite the French, and try to win round those who voted against him.
More than 3,000 police have been deployed in Paris and its multi-ethnic suburbs in case Mr Sarkozy's victory sparks a repeat of the riots seen in 2005.
French pundits greeted the strong turnout as a victory for French democracy.
Both candidates worked hard to woo the supporters of the third-placed candidate in round one, centrist Francois Bayrou.
Polls suggest that they each won over 40% of the Bayrou voters, and that 20% did not cast a ballot in round two.