Mbappe’s first-half brace was cancelled out by the hosts.
PSG have been stunned by Monaco, who produced an incredible comeback to grab three points.
Kylian Mbappe opened the account for the visitors in the 25th minute after he was picked out by Angel Di Maria on the counter.
Shortly after, the French World Cup winner doubled the lead from the penalty spot after a foul on Rafinha.
Mbappe almost got his hat trick when his goal was disallowed by VAR.
Monaco picked up the pace from the very beginning in the second half when Kevin Volland’s strike beat past Keylor Navas.
The German striker soon found the equaliser, assisted by Cesc Fabregas, who was substituted in the second half.
Things got worse for Les Parisiens after Abdou Diallo made a silly foul in Monaco’s penalty box for which he received a red card. Fabregas successfully converted the penalty, which turned out to be the winning goal for Niko Kovac’s side.
Neymar also made his return from injury in the second half but the Brazilian couldn’t help PSG from falling apart.
Fabregas stole the show with his heroics in the second half – a goal and an assist – which helped Monaco to get into the second position in the league table.
Elsewhere, Thomas Tuchel has been put under scrutiny once again for leading his side to the third defeat in Ligue 1 this season. The German manager also received a lot of stick for the Champions League defeats against Manchester United and RB Leipzig.