French Interior Minister Cazeneuve replaces Valls as PM
French Interior Minister Bernard Cazeneuve has been named as prime minister, replacing Manuel Valls, who resigned in order to make a bid for the presidency next year.
Mr Valls presented his resignation to President Francois Hollande on Tuesday.
Mr Cazeneuve will be in charge of the Socialist government until June's parliamentary elections.
He has played a key role in managing France's security since the jihadist terror attacks in Paris last year.
Mr Valls will face other contenders in the Socialist primary next month.
Last week, in a move that surprised many, President Hollande announced that he would not seek a second term.
He is the first president since France's Fifth Republic was created in 1958 not to seek a second mandate. But he has haemorrhaged support amid stubbornly high unemployment and anxiety about Islamist terror.
If successful, Mr Valls will face Francois Fillon and Marine Le Pen in the first round of the presidential election in April.
Current polling suggests that Ms Le Pen, leader of the far-right National Front (FN), could come in the top two in the first round, but would be likely to lose to the centre-right Mr Fillon in the second.
Mr Valls is not guaranteed to win the Socialist primary, which will involve at least seven other candidates. They will include former economy minister Arnaud Montebourg, who is further to the left.
Mr Valls is seen as a divisive figure on the left, after forcing labour reforms through parliament and endorsing controversial bans last summer on the Islamic "burkini" swimsuit.
Even if he wins the primary, he could be undermined by two rivals for leftist or centrist votes: the radical socialist Jean-Luc Melenchon and centrist Emmanuel Macron, a former economy minister.
The new interior minister, replacing Mr Cazeneuve, is Bruno Le Roux. He is the Socialist parliamentary leader and another close ally of President Hollande.
Mr Cazeneuve, 53, was a spokesman for Mr Hollande during the 2012 presidential campaign that brought victory for Mr Hollande over Nicolas Sarkozy.
In 2012-2013, Mr Cazeneuve was junior minister for European affairs. That post included the difficult task of getting parliamentary approval for the EU's European Stability Mechanism, despite opposition from some fellow Socialists.
In 2013-2014 he was junior minister for the budget. France's Le Parisien daily says his command of tough budgetary issues earned him the nickname "R2D2" - referring to a robot in the original Star Wars film.
He became interior minister in 2014 when the incumbent, Jerome Cahuzac, resigned because it was revealed that he had a secret Swiss bank account.
Mr Cazeneuve faced a stormy period of national trauma for France, as attacks linked to so-called Islamic State (IS), in Paris and Nice, claimed 238 lives.
The Nice attack, when a lorry ploughed into a crowd of revellers on the beachfront, put Mr Cazeneuve under fire for alleged policing failures.
He has overseen the state of emergency imposed after last year's Paris attacks, including extra surveillance of suspected jihadists and extra powers for police to conduct searches.
In recent months he has had to deal with discontent among police officers, who say the state has left them under-resourced, considering the scale of the terror threat.
The son of a schoolteacher, Mr Cazeneuve was born in Senlis, northern France, and trained as a lawyer.
French media see Cazeneuve as reliable loyalist - BBC Monitoring
Several French media outlets note that Mr Cazeneuve is regarded very much as a safe pair of hands by President Hollande, who has come to rely heavily on his loyalty, discretion and reliability.
Le Monde also says that over the past few years, Mr Cazeneuve "has established himself as one of the key pieces on Hollande's chessboard".
Liberation notes that Mr Cazeneuve's "trademark" characteristic is his ability to remain calm in the heat of a crisis.
However, several outlets - including Le Point magazine and BFMTV - predict that Mr Cazeneuve is likely to spend only a record-breaking short term of five months in his new role before the 2017 presidential election.