Ducati's Francesco Bagnaia got the measure of six-time world champion Marc Marquez in a gripping duel to win the Aragon MotoGP from pole on Sunday.
Yamaha's Fabio Quartararo retained the world championship lead despite finishing down the field in eighth.
SA's Brad Binder finished seventh after starting 12th on the grid on Sunday.
This was Bagnaia's debut success in the premier category after 10 wins combined in Moto2 and Moto3.
After nailing pole position with a track record time on Saturday Bagnaia led from the start tracked by Marquez, who was hunting his 58th MotoGP win.
The pair soon pulled clear of the pack with Marquez launching multiple attacks over the closing laps.
On his last passing attempt the Spaniard born not far from the circuit went too wide on the turn, allowing Bagnaia to take a hard-fought but deserved first MotoGP win.
"This victory today is like a release. We've worked hard to get this result," said Bagnaia.
Defending champion Joan Mir came third.
With five rounds of the season to go Quartararo leads the race for the riders' crown on 214 points, with Bagnaia in second on 161 and Mir four points further adrift.