In Paris hundreds of people have been gathering every night since 31 March in the city's Place de la Republique.
They stay there until dawn, when police come to disperse them.
Although France's labour reforms is a unifying theme of the "Up All Night" gatherings, the movement embraces a range of anti-establishment grievances. An organiser told French news agency AFP the aim was to "build a strong social movement that brings together all those in precarious situations against the oligarchy", describing the goal as "very ambitious".
Students have been at the forefront of weeks of sometimes violent protests over the Socialist government's labour reforms, which will make it easier for struggling companies to fire people.
The government says the reforms will help rein in youth unemployment, which currently stands at around 25 per cent.
Meanwhile on Wednesday night, the "Nuit Debout "("Up All Night") movement spread across the border to Belgium, as a couple of hundred people turned out onto the streets of Brussels.
"Up All Night" protesters say they are drawing inspiration from the Spanish protesters known as the Indignados, who gave rise to the far-left Podemos party.
Tens of thousands of Indignados occupied Madrid's Puerta del Sol square in 2011 in protests against growing inequality, spending cuts and corruption.
Podemos MEP Miguel Urban Crespo was among around 1,000 people who turned out for Tuesday night's protest in Paris.
In addition to the protests in Paris, hundreds of young people in Nantes and Rennes began protesting on Tuesday. This followed clashes between mainly young people and riot police last week during protests against the planned labour law.
The movement kicked off Tuesday as well in Toulouse, gathering some 300 people vowing to "bring struggles together".
On Wednesday French government spokesman Stephane Le Foll played down the importance of the protest movement while saying it deserved "respect".