All schools and non-essential shops will shut for four weeks, and a curfew will be in place from 19:00 to 06:00.
On Friday, the number of seriously ill Covid patients in intensive care units (ICU) increased by 145 - the biggest jump in five months.
President Emmanuel Macron has promised more hospital beds for Covid patients.
France is currently battling a peak of about 5,000 Covid patients in ICUs. On Friday, the country recorded 46,677 new cases and 304 deaths.