France's Interior Ministry said more than 600,000 people took to the streets on Thursday while the CGT, one of France's major unions, said nearly 1.6 million people took part in more than 200 demonstrations nationwide.
The figures exceed those reported on October 17, when protests were marred by scenes of rioting and looting.
The Paris march proceeded peacefully, with students, workers and retirees joining in. Some young demonstrators were carrying signs reading: "Inequalities seriously jeopardise our future" and "We can't spend our whole lives just trying to make a living."
The CGT, which estimated 350,000 marched in Paris, said the turnout marked a new stage in the mobilisation and vowed to "continue its fight for as long as necessary to force the government and employers to give in to its demands".
About one-third of France's high schools were closed or unable to operate, some because of student blockades and others because teachers were on strike. Public transportation was disrupted in some areas. The Eiffel Tower was also closed.
Interior Minister Laurent Nuñez said 70,000 police officers were deployed, backed by armoured vehicles, drones and helicopters. Police have been criticised for injuring protesters with heavy-handed tactics.
Authorities in the western region of Brittany said masked individuals tried to block roads in Rennes. They said young people, often accompanied by adults, committed "serious acts of violence," including throwing steel balls at police.
Authorities also reported tensions, scuffles and other incidents in the cities of Lyon, Nantes, Pau, Orléans, Rennes and Toulouse.
Large, recurring protests in recent weeks have been marred by violence, which authorities blamed on masked far-left radicals seeking to incite insurrection and others intent on looting.
France's main unions warned the country is on the brink of recession and that layoff plans are multiplying.
"Fuel, food products, rent, gas, electricity … everything's going up except wages and pensions," they said in a joint statement.
France is mired in debt and is one of the worst economic performers in Europe, along with Italy and Belgium.
The movement began in September with a protest over staff shortages at a high school southeast of Paris and spread nationwide. It drew students demanding more education funding and then broadened to workers seeking better pensions and help with soaring fuel prices and other costs.
