Union leaders claim as many as 2.5 million people took to the streets as France saw its first big strike triggered by the global credit crunch. French police put the number at just over one million.
In Paris, tens of thousands marched from Place de la Bastille to the centre of the capital, some carrying lighted flares.
Platforms at St Lazare station, Paris, and elsewhere stood deserted as rail services were hit by strike action.
This demonstrator in Nice carried a placard calling for President Nicolas Sarkozy to resign.
A protester in Paris donned a Sarkozy mask and held a placard reading "Hello - Beat it, loser" - words the president famously snapped at a hostile member of a crowd during a walkabout last year.
Demonstrators in Lyon carried a red banner calling for "Neither state nor bosses - revolution!"
Other demonstrators in Lyon "mourned" the loss of civil liberties and the privatisation of hospitals and postal services.
Large numbers of strikers thronged the Old Port at the heart of Marseille, the biggest city in southern France.
In Paris, some of the protesters threw stones and set fire to rubbish bins.
Police had to use tear gas to dispel the crowd of youths.