Edouard Philippe said the country was “cut in two” in terms of the rate of infections. Restrictions will remain in the capital and north-eastern regions.
It comes as France prepares to relax its lockdown on Monday, with shops and some schools allowed to reopen.
The country has suffered one of the highest Covid-19 death rates in Europe.
More than 25,800 people there have died from the disease in hospitals and care homes, but the number of new cases has also fallen in recent days.
Restrictions – introduced on 17 March – would be lifted over the course of several weeks, Prime Minister Philippe said on Thursday.
“It’s good news for France and for the French people,” he said.
The government has issued a colour-coded map of the country, splitting it into green and red areas depending on the rate of infection. Restrictions will be eased more in the green areas than the red for the time being.
To begin with, primary schools and most businesses will be allowed to reopen in both zones. Cafes, restaurants and secondary schools will be able to reopen in June in the green zones, infection rates permitting, Mr Philippe said.
In Paris and the four adjoining regions – Ile-de-France, Hauts-de-France, Grand Est Bourgogne-Franche-Comte – which comprise the red zone, public parks and gardens will stay shut.