Emmanuel Macron became France's youngest ever president yesterday, promising at his inauguration to restore the country's lost confidence and pledging to relaunch the flagging European Union.

Macron, a 39-year-old centrist, took the reins of power from Socialist Francois Hollande at the Elysee Palace a week after his resounding victory over far-right leader Marine Le Pen in an election that was watched worldwide.

Macron said his first priority would be "to give back to the French people the confidence that for too long has been flagging", while the second would be making France a beacon for democracy and freedom worldwide.

France's place was in the European Union "which protects us and enables us to project our values in the world," but he said the 28-member bloc needed to be "reformed and relaunched."

Macron also suggested he would press on with his ambitious but controversial agenda to reform France's rigid labour market and modernise the social security system despite the fierce resistance he is likely to meet.

"I will not reverse course on any of the commitments taken in front of the French people," he said, adding that "France is strong only if she is prosperous."

Some analysts and opponents have questioned the strength of Macron's mandate after he won just 24.01 percent in the first round of the presidential election on April 23 before his landslide victory over Le Pen in the second.

His opponents on the far-right and far-left, opposed to the EU and major economic reforms, won around 50 percent of the first-round vote.

The new president faces a host of daunting challenges including tackling stubbornly high unemployment, fighting Islamist-inspired violence and healing divisions exposed by an often vicious election campaign.

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.

Macron's first week will be busy. Today, he is expected to reveal the closely-guarded name of his prime minister, before flying to Berlin to meet German Chancellor Angela Merkel.