French Economy Minister Emmanuel Macron has resigned from the government ahead of an expected centrist bid for the presidency in next year's election.
The 38-year-old former investment banker has been a controversial figure in Socialist President Francois Hollande's government.
He has questioned France's 35-hour work week and blamed high unemployment and weak economic growth on a lack of competitiveness.
He will be replaced by Michel Sapin.
The move was announced by Mr Macron himself in a message to supporters, and by the French presidency.
However, Mr Macron stopped short of formally declaring a 2017 presidential bid.
In a speech to ministry staff, he said he had resigned to focus on drawing up a "diagnosis" of the country's problems.
"I am determined to do everything so that our values, our ideas, our actions can transform France as soon as next year," he added.
President Hollande picked Mr Macron, then a relative unknown, to join his government in 2014.
His first big test as economy minister was to introduce reforms including allowing shops to open more often on Sundays, a move that led to protests.
Prime Minister Manuel Valls forced the so-called "Macron Law" through parliament without a vote to prevent left-wing rebels scuppering it.
Colourful personal life
Correspondents say Mr Macron has won support from the young and cosmopolitan - what Le Monde terms the "winners from globalisation".
He ruffled feathers in the Socialist Party earlier this year by setting up a new political movement "En Marche" (On the Move), and has upset trades unions by calling for further, more radical labour reforms and by lauding entrepreneurs.
Responding to criticism from within his own party last year, he said: "If approval was a criterion in this country, nothing would ever get done."
His speeches to supporters have broadly hinted at his presidential ambitions, and he routinely polls higher than Mr Hollande.
His personal life is, if anything, even more colourful.
At the age of 17, he began a relationship with a teacher at his high school, a woman 20 years his senior, to whom he is now married.