Head coach Zinedine Zidane led Les Bleus to a 1-0 Nations League win against Turkey at Yildiz Entegre Kocaeli Stadyumu on Friday where the Real Madrid attacker injured himself as he scored the game's only goal in the 54th minute.
Mbappe battled on for another few minutes before being replaced by Desire Doue.
Real have games against Villarreal, Roma, Sevilla, RB Leipzig and Barcelona in the month of October and will certainly feel the Frenchman's absence, following his eight goals in eight appearances across all competitions for Jose Mourinho's side this season.
A French Football Federation statement read: "After the tests carried out today on our player Kylian Mbappe by Real Madrid's Medical Services, he has been diagnosed with a hyperextension of the posterior capsule of his left knee. Awaiting evolution."
"No, it's not good. It's not good, unfortunately," Zidane told French television. “He will have to go back. We will not take risks, he has extended his knee when he took the shot. It's not very encouraging.”
Real Madrid president Florentino Perez has been summoned to appear in a Madrid court after Barcelona took legal action over comments he made about the club and the refereeing scandal.
Michael Olise produced a stunning late solo goal to give France a 1-0 UEFA Nations League victory over Belgium, sending coach Zinedine Zidane into wild celebrations on the touchline.
France left it late against Belgium as Michael Olise came off the bench to score an 88th-minute winner, while Italy produced a powerful response by beating Turkey 4-1 in the UEFA Nations League.
Kylian Mbappe says his African heritage remains an important part of his identity and that, if he wins the Ballon d'Or for the first time, he would dedicate the achievement in part to the continent.
