Yamaha's French world championship leader dedicated the win to Dupasquier, 19, who died in hospital of injuries sustained in a multi-bike crash in qualifying on Saturday.
Quartararo crossed the line with plenty of daylight back to reigning world champion Joan Mir in second, with Portugal's Miguel Oliveira completing the sombre podium.
We’re deeply saddened to report the loss of Jason Dupasquier
— MotoGP™?? (@MotoGP) May 30, 2021
On behalf of the entire MotoGP family, we send our love to his team, his family and loved ones
You will be sorely missed, Jason. Ride in peace pic.twitter.com/nZCzlmJsVi
The sixth leg of the season was totally overshadowed, however, by the death of Dupasquier - the sport's first fatality since Luis Salom died in practice at the Catalonia Moto2 Grand Prix in Barcelona in 2016.
South Africa's Brad Binder finished fifth after starting sixth on the grid.
? @marcmarquez93 tumbles out on Lap 2!#ItalianGP ???? pic.twitter.com/nARUm7Ahbf
— MotoGP™?? (@MotoGP) May 30, 2021
Your #ItalianGP ???? Podium
— MotoGP™?? (@MotoGP) May 30, 2021
?? @FabioQ20
?? @_moliveira88
?? @JoanMirOfficial #MotoGP ?? pic.twitter.com/fHIbRbAfMR