Niger’s military junta that seized power last month on Thursday said it had revoked the French ambassador’s diplomatic immunity and instructed the police to expel him.
Sylvain Itte visa and that of his family have also been cancelled.
He had been told by the junta last Friday that he had 48 hours to leave the country in response to actions taken by the French government which it said were "contrary to the interests of Niger".
But the deadline passed on Monday without Paris recalling him.
French President Emmanuel Macron said on Monday that the ambassador would stay in Niger despite pressure from the military regime. And he reiterated Paris' support for ousted democratically-elected president Mohamed Bazoum.
The French government said it does not recognise the coup leaders as the country's legitimate rulers.
Since toppling the president, the junta has leveraged anti-French sentiment among the population to shore up its support.