French authorities have estimated that nearly one million protesters filled the streets to try to force President Nicolas Sarkozy to drop his plan to raise the retirement age by two years to 62, while strikes also disrupted airports, train stations and schools for the second time this month.
The protest movement has been a big test for Mr Sarkozy, who, like other European leaders, has struggled to convince his country of the need for cost-cutting and scaling back generous social benefits after the Greek debt crisis scared markets and sapped confidence in the entire 16-nation euro currency.
France's powerful unions consider retirement at 60 to be a near-sacred right, and more than 230 demonstrations stretched from the southern port city of Marseille to Lille in the north. Some protesters carried signs demanding early retirement for Mr Sarkozy, whose dismal approval ratings hover in the mid-30s.
With stakes high, the government and unions disagreed about the size of the turnout - even more so than usual.
The Interior Ministry said the protest movement had lost steam since the last day of protests on September 7, with 997,000 protesters in the streets, a drop of about 11%. But unions said the movement grew to nearly 3 million protesters, up from what they said was about 2.5 million last time.
In Paris, one protester carried a sign reading "Austerity? For the rich first!". Vendors at the Bastille sold vuvuzelas - a new noisemaker for French demonstrators, joining the traditional megaphones and whistles.
Some retirees were marching out of solidarity for youths.
"Today we have a pension, we deserve one, and we wish the same thing for the younger generation," said retired police officer Michel Fourgues.
As baby-boomers reach retirement age and life expectancy increases in France, the conservative government insists it must raise the retirement age so the money-losing pension system can break even by 2018.
Mr Sarkozy has indicated he is willing to make marginal concessions but remains firm on the central pillar: increasing the retirement age from 60 to 62 and pushing back the age from 65 to 67 for those who want full retirement benefits.