More than two million people are expected to take to the streets across France today in protest over Nicolas Sarkozy's pension reform plans.
Action on the public transport network began on Monday night and severe disruption is likely across the country.
The French parliament today begins a debate over the plan to overhaul the pension system which will see the minimum retirement age raised from 60 to 62 years by the year 2018.
Bernard Thibault, head of the CGT union, the country's largest, said he believed even more people would turn out than in June, when more than 800,000 took part in demonstrations.
Schools are also expected to be affected badly by the mass walkout - the third of its kind since the start of the year.
All the main trade unions are urging private and public sector staff to join the stoppage to press the government into withdrawing its plans.
The government has suggested it might make some concessions but, after France's failure to embrace economic reforms to slash its deficit, works minister Eric Woerth is under intense pressure to proceed with the main elements of the overhaul.
In February, the French government has said its pension deficit will be 10.7bn euros ($14.6bn; £9.3bn) this year, and rise to 50bn euros by 2020.
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