Prime Minister Jean Castex said the measures will not be as strict as the previous lockdown, with people allowed to exercise outdoors.
Mr Castex said a “third wave” of infections in the country was now looking increasingly likely.
The virulent variant first detected in the UK is now accounting for some 75% of cases in the country.
Intensive care wards are under severe strain, notably in Paris where the incidence rate surpasses 400 infections in every 100,000 inhabitants.
“The epidemic is getting worse. Our responsibility now is to not let it escape our control,” Mr Castex told a news conference.
France reported 35,000 new cases on Thursday and there were more Covid patients in intensive care in Paris than at the peak of the second wave,
Now is the time to tighten restrictions, Mr Castex said.
“Four weeks, the time required for the measures to generate a sufficient impact. (It is) the time we need to reach a threshold in the vaccination of the most vulnerable.”
The lockdowns will kick in from Friday at midnight in France’ 16 hardest-hit departments that, with the exception of one on the Mediterranean, form a corridor from the northern Channel port city of Calais to the capital.
Barbers, clothing stores and furniture shops will have to close, though bookstores and others selling essential goods can stay open.
Schools will stay open and people will be allowed to exercise outdoors within a 10 km radius of their homes.
Travel out of the worst-hit areas will not permitted without a compelling reason.
“Go outdoors, but not to party with friends,” the prime minister said.