Earlier, Anthony Martial gave United the lead after latching onto Andreas Pereira's pass but Lucas Moura's deflected effort in the second-half made it 1-1.
The victory is PSG's fifth in a row to start the Ligue 1season, and takes them three points clear at the top of the fledgling table, ahead of champions Monaco, who play Nice on Saturday.
Mbappe, who has scored four goals and provided four assists in 11 games for the Ligue 1 club this season, burst ontothe world stage with Monaco last season.
"They are going to create chances and put teams under pressure all day long, every time they step ontothe field, regardless of the opposition. "But I tell you what, and they give me a heart attack at the back.
Manchester United manager, Erik ten Hag has explained why he stormed ontothe touchline to berate Anthony Martial during their 1-0 defeat to Newcastle on Saturday.
Miguel Almirón scored on his return to Atlanta to earn Newcastle United a 1-1 draw with Chelsea in the Premier League clubs' preseason friendly at Mercedes-Benz Stadium on Wednesday.
"In the end I got minutes again and I played well towards the end of theseason, so I just have to get my head down and get to work. "It is not going to be easy here, but it was never going to be easy," the American added.
"We talked together in the dressing room about Arsenal-Tottenham. Both lost two points. "Top four is a hard war, because we're not only four teams, we're six teams. "Now we have 11 games to play till the end of theseason.
Mourinho worked as an interpreter for Bobby Robson during the Englishman's time in charge of Barcelona, with Ronaldo among those brought ontothe books at Camp Nou.
Five minutes later and PSG got their second after Dembele's strike was saved by Maignan but tapped in by Kolo Muani on the rebound. Maignan tipped a late Mbappe strike ontothe post as the 2020 finalists finished strongly.
The Hatters lost 2-1 in North London to Tottenham Hotspur after failing to hold onto a 1-0 lead against Tottenham, while Mikel Arteta's tenacious team salvaged a commendable point from Manchester City.
Chukwueze was stretchered off with an injury on the half-hour mark in the return leg at the Emirates, but Emery's side held onto a 0-0 draw to send them through to the final.