Emmanuel Macron was inaugurated as France's youngest ever president on Sunday, saying the country had chosen "hope" and promising to relaunch the flagging European Union.
Macron, a 39-year-old centrist, took the reins of power from Francois Hollande a week after he won a resounding victory over far-right leader Marine Le Pen in a tumultuous election.
After a warm welcome from Hollande at the Elysee Palace, the two men held a closed-doors meeting during which Macron was handed the codes to launch France's nuclear arsenal.
In a moment heavy with symbolism, 62-year-old Hollande - who launched Macron's political career by appointing him first as advisor and then economy minister - was then driven away from the palace to applause from his staff and the new president.
The former investment banker who had never even contested an election before was then proclaimed president by Laurent Fabius, president of the Constitutional Council.
"In order to be the man of one's country, one must be the man of your time," Fabius told him.
"You are now the man of your time ... and by the sovereign choice of the people, you are now, above all ... the man of our country."
Watch: Macron unveils En Marche candidates
In his first speech, Macron said the French people had chosen "hope" and shown a willingness to change in the election.
He promised that the EU, hit by the imminent departure of Britain, would be "rejuvenated and relaunched" during his time in office.
"The world and Europe need France now more than ever and they need a strong France with a sense of its own destiny."
To underline his European ambitions, Macron will visit German Chancellor Angela Merkel in Berlin on Monday in his first foreign trip.
The new president's wife Brigitte, a 64-year-old who was his high school drama teacher, listened to his sombre 12-minute speech wearing a light blue Louis Vuitton outfit.
At the end of the formalities, a 21-gun salute rang out from the Invalides military hospital on the other side of the River Seine.
Republican guards arrive for Emmanuel Macron's formal inauguration ceremony as French President. Source: AP
Macron was later to be driven to the Arc de Triomphe to lay a wreath at the tomb of the unknown soldier.
The new president faces a host of daunting challenges including tackling stubbornly high unemployment, fighting Islamist-inspired violence and uniting a deeply divided country.
Socialist Hollande's five years in power were plagued by a sluggish economy and bloody terror attacks that killed more than 230 people and he leaves office after a single term.
Security was tight, with around 1,500 police officers deployed near the presidential palace and the nearby Champs Elysees avenue and surrounding roads blocked off.
After a formal lunch, Macron will visit Paris's town hall, a traditional stop for any new French president in his "host" city.
PM named, then Berlin
Macron's first week will be busy. On Monday, he is expected to reveal the closely-guarded name of his prime minister, before flying to Berlin.
It is virtually a rite of passage for French leaders to make their first European trip to meet the leader of the other half of the so-called "motor" of the EU.
Pro-EU Macron wants to push for closer cooperation to help the bloc overcome the imminent departure of Britain, another of its most powerful members.
He intends to press for the creation of a parliament and budget for the eurozone.
Merkel welcomed Macron's decisive 32-point victory over Le Pen, saying he carried "the hopes of millions of French people and also many in Germany and across Europe".
The red carpet is set up prior to the takeover ceremony between President Francois Hollande and President-elect Emmanuel Macron. Source: AP
In June, Macron faces what the French media are calling a "third round of the presidential election" when the country elects a new parliament in a two-round vote.
The new president needs an outright majority to be able to enact his ambitious reform agenda.
The year-old political movement "Republique en Marche" (Republic on the Move, REM) that he formed to launch his presidential bid intends to field candidates in virtually every constituency in the country.
It unveiled 428 of its 577 candidates this week, saying it wants to bring fresh faces into the National Assembly lower house of parliament.
Half of them have never held elected office, including a retired female bullfighter and a star mathematician, and half of them are women.
Macron won one of the most unpredictable French elections in modern history marked by scandal, repeated surprises and a last-minute hacking attack on his campaign.
The election saw voters reject France's two traditional political forces of left and right. Their candidates were eliminated in the first round.
Unpopular Hollande was the first to bow to the rebellious mood in December as he became the first sitting president not to seek re-election in the French fifth republic, founded in 1958.
