Former French premier Manuel Valls can not run for parliament for president-elect Emmanuel Macron's En Marche!
Hollande accepted the resignation and asked Cazeneuve in a letter to handle affairs until the formation of a new government team, according to an Elysee statement.
The US political establishment gave a broad welcome Monday to France's election of Emmanuel Macron, taking a cue from President Donald Trump who had kept his distance from Marine Le Pen despite his supporters' enthusiasm for her.
With legislative elections just five weeks away, the start-up political movement the 39-year-old former investment banker launched one year ago on his meteoric ride to become France's youngest president lost no time Monday in girding for the crucial mid-June election battle.
Le Pen, who came third in the 2012 presidential election, has spent years planting a grassroots structure for her party. All 577 seats in the Assembly are up for grabs.
As economy minister, a post he held for two years from August 2014, Macron had called for the merger of French auto giant Renault SA and its Japanese partner, Nissan Motor Co.
The Socialists are torn between the radical left of their defeated candidate Benoit Hamon and the more centrist, pro-business branch led by Manuel Valls, who was prime minister under Hollande.
In an early plea for unity, Macron reached out to Le Pen's supporters after a vicious election campaign that exposed deep economic and social divisions, as well as tensions provoked by identity and immigration.
Macron rejected Le Pen's plan to strip dual-nationals convicted of terror offenses of French nationality on rights grounds.More news: Vettel still confident despite Hamilton's win at Spanish GP
Obama's Republican successor sent out an ebullient tweet about Macron's win 82 minutes after the results were announced Sunday, saying "I look very much forward to working with him!"
Macron's optimistically named "En Marche!" Macron has promised that half of those candidates would be new to elected politics, as he was before his victory on Sunday.
How his presidency plays out and how markets move on in the months ahead could rest on June elections to the French parliament.
The scant coverage from mostly French-language media estimated that the demonstrators calling for Macron's resignation numbered in the thousands.
The anti-European Union, anti-immigration Ms Le Pen said the election pitted "patriots" against "globalists" after candidates from the traditionally dominant socialist and conservative parties were eliminated in an April 23 first-round vote.
If they win a majority, Francois Baroin, the leader of their parliamentary election campaign, could become a right-wing prime minister under the centrist Macron.
The CAC 40 index of leading French shares fell 0.9 percent to 5,383.
Macron's victory has therefore pushed back any fear that France was on a road that could have led to the breakup of the European Union and the euro itself.