Update - 10.40am: Emmanuel Macron has been sworn in as France's new president and immediately pledged to do everything necessary to fight terrorism.
In a ceremony at the Elysee presidential palace in Paris, the 39-year-old took over the reins of power from Francois Hollande.
Mr Macron, who is the youngest president in the country's history, said in his inauguration speech: "We will take all our responsibilities to provide, every time it's needed, a relevant response to big contemporary crises."
He also listed "the excesses of capitalism in the world" and climate change among his future challenges.
All countries in the world are "interdependent ... we are all neighbours," he said.
And he announced his determination to push ahead with reforms to free up France's economy and pledged to press for a "more efficient, more democratic" European Union.
Mr Macron takes charge of a nation that, when Britain leaves the European Union in 2019, will become the EU's only member with nuclear weapons and a permanent seat on the UN Security Council.
His Republic on the Move movement hopes to reinvigorate French politics and win a majority of lawmakers in the June parliamentary election.
Mr Hollande was loudly applauded by the employees of the French presidency as he left the palace. He shook hands with Mr Macron, who accompanied him to his car and also applauded him.
The new president then posed for photographers at the front porch of the Elysee with his wife, Brigitte.
Mr Macron had been Mr Hollande's top economy adviser from 2012 to 2014, then became his economy minister until last year, when he decided to quit the Socialist government and launch his independent presidential bid.
Earlier: France's Emmanuel Macron has arrived for his inauguration ceremony at the Elysee presidential palace in Paris, ready to fully embark on his mission to shake up the world of French politics.
His predecessor, Francois Hollande, welcomed him in the courtyard, shaking hands in front of hundreds of journalists.
The two were meeting in the president's office before Mr Hollande's departure, taking a last few minutes to discuss the most sensitive issues facing France, including the country's nuclear codes.
Mr Macron takes charge of a nation that, when Britain leaves the European Union in 2019, will become the EU's only member with nuclear weapons and a permanent seat on the U.N. Security Council.
He will then make a speech in the Elysee reception hall in front of about 300 guests, officials and family members, including his wife Brigitte Macron.
Outside the Elysee, a few dozen supporters waved French tricolor and European blue flags at the arrival of the new president.
Following the ceremony and military honours at the Elysee palace, Mr Macron will go the Tomb of the Unknown soldier, at the Arc de Triomphe at the top of the Champs-Elysees Avenue, a tradition followed by all heads of states in France's modern history.
He will also meet with Paris Mayor Anne Hidalgo later on Sunday.
On Monday he travels to Germany to meet German Chancellor Angela Merkel in Berlin and then in the following days will have to name his prime minister and form a government.