Real Madrid lost the round of 16 first leg 1-0 at the Parc des Princes thanks to Mbappe’s brilliant winner in second half stoppage time.
The 23-year-old was a constant thorn in Real Madrid’s flesh throughout the game as he forced Thibaut Courtois into a number of saves and won a penalty which was missed by Lionel Messi.
Ancelotti has admitted that Mbappe was unstoppable on the night and his defenders could not cope.
"Mbappe is unstoppable," Ancelotti was quoted as saying by Marca.
"We have tried to control him. [Eder] Militao has done very well but [Mbappe] can always invent something out of nothing, and he created at the last minute."
Real Madrid failed to record a single shot on target in the entire game.
Explaining their issues, Ancelotti continued: "We've done quite well in defence but we haven't been very aggressive.
"We lacked something with the ball, we've missed many passes and it took a lot to get out of their pressure.
"[Marco] Asensio and Vini [Vinicius Junior], [Karim] Benzema as well, they didn't get many balls. With the ball we didn't do as we wanted.
"We tried to start from the back but it didn't work out. The low block had to be more aggressive, but it wasn't a conservative approach. It didn't work out for us, getting the ball as we know."
