Quartararo, 21, who rides for the Yamaha satellite outfit, had started on pole position and his biggest threat, reigning world champion Marc Marquez, crashed out on lap 20.
“It’s the most beautiful day of my life,” an ecstatic Quartararo said as his team celebrated.
Marquez had already come off the track on the fourth lap of a race held in sweltering conditions but just managed to hold on and got back in contention.
But worse was to come on the 20th lap when the Spaniard, who was lying third, lost control and came off his bike which then appeared to hit him as man and machine bounced across the infield shale.
The first race of a season delayed and truncated by the coronavirus pandemic was run without spectators and the riders observed a minute’s silence before the race in memory of the victims of the virus.
Italian MotoGP great Valentino Rossi came off on lap 19 when in tenth place, crushing his hopes of scoring points in the opening race of the season.
Rossi, the 41-year-old nine-time world champion, has already been told he will be replaced in Yamaha’s main team next year when Quartararo steps up from Yamaha SRT.
There was some success for the Rossi family though when his half-brother Luca Marini won the Moto2 race in Jerez.