It is a mobilisation the French unions had been hoping for.
Police figures show that more than 1.1 million took part in nationwide protests against pension reforms.
Union estimates put the total as high as 2.7 million.
It is a massive show of force against the government’s plan to raise the retirement age from 60 to 62.
And there are warnings that further days of action are planned.
Jean-Claude Mailly, the Secretary General of the FO union, said: “If the government doesn’t quickly respond to this action, a follow-up is needed. It’s not a case of today we protest, we show we’re unhappy and then we all go home.”
There was widespread disruption to public transport and other services, as workers heeded union calls to go on strike.
Socialist Party leader Martine Aubry said: “The government wants to mix everything up to have us believe that we’re not as well off as other countries. It’s totally false. If this reform goes through, we will have one of the toughest systems in Europe.”
But despite the massive demonstrations, the government says it will not back down on the main thrust of its reforms.