Fabio Quartararo became the first French rider to win a Moto Grand Prix since 1999 as he took the flag in the season-opening race in Spain on Sunday after Marc Marquez had a heavy crash and broke a bone in his arm.
Quartararo, 21, who rides for the Yamaha satellite outfit, had started on pole position and his main threat was removed when reigning world champion Marquez crashed out on lap 20.
"It's the most beautiful day of my life," an ecstatic Quartararo said as his team celebrated.
"We need to enjoy this, it's not every day you have your first MotoGP victory!" he added.
Six-time world champion 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 get 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 hit him on the arm as man and machine bounced across the infield gravel.
Marquez was taken away from the track in an ambulance and his Repsol Honda team later said he had broken his right humerus and would require an operation.
"A fall at Turn 3 while fighting for the podium has resulted in a broken right humerus for @marcmarquez93, who will travel to Barcelona for surgery," the team tweeted.
Yamaha rider Maverick Vinales took second place and Ducati's Andrea Dovizioso was third.
The first race of a season delayed and truncated by the coronavirus pandemic was run without spectators. The riders observed a minute's silence before the start in memory of victims of the virus.
Marquez has already earmarked Quartararo as his most serious challenger this season and this first victory for a Frenchman in MotoGP since Regis Laconi in Valencia in 1999 will only confirm that view.
Quartararo used the cornering ability of the Yamaha to pull away from his rivals and had stretched his lead to as much as six seconds at one point.
His victory was the first for a Yamaha satellite team in MotoGP.
Along with Marquez, it was also a bad start to the season for Italian great Valentino Rossi as he came off on lap 19 when in tenth place, crushing his hopes of scoring points.
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.
The next MotoGP will take place on the same Jerez circuit next Sunday.