Spain's Jorge Lorenzo claimed his first win for Ducati at the Italian Grand Prix as championship leader Marc Marquez crashed out in Mugello.
Three-time champion Lorenzo has struggled since leaving Yamaha in 2016 but beat team-mate Andrea Dovizioso.
Seven-time world champion Valentino Rossi become the first rider to reach 5,000 points in MotoGP with third.
"It's special to win here with Ducati," said Lorenzo, who has retired from two races this season.
Marquez crashed before finishing 16th in Tuscany, though he remains comfortably clear of the standings after five races.
The Spaniard had been bidding for his fourth straight win this season but fell off his Honda on the fifth lap.
Rossi moves up to second in the standings, 23 points behind Marquez, with Yahama team-mate Maverick Vinales in third.
"It was my goal to return to the podium at Mugello, I'm very happy," said Rossi, who had started on pole.
Italian Grand Prix result:
1 Jorge Lorenzo (Spa/Ducati) 41mins 43.230secs
2 Andrea Dovizioso (Ita/Ducati) +6.370secs
3 Valentino Rossi (Ita/Yamaha) +6.629secs
4 Andrea Iannone (Ita/Suzuki) +7.885secs
5 Alex Rins (Spa/Suzuki) +7.907secs
6 Cal Crutchlow (GB/LCR Honda) +9.120secs
7 Danilo Petrucci (Ita/Ducati Pramac) +10.898secs
8 Maverick Vinales (Spa/Yamaha) +11.060secs
9 Alvaro Bautista (Spa/Ducati) +11.154secs
10 Johann Zarco (Fra/Yamaha Tech3) +17.644secs
Championship standings (after six of 19 races):
1 Marc Marquez (Spa/Honda) 95 points
2 Valentino Rossi (Ita/Yamaha) 72
3 Maverick Vinales (Spa/Yamaha) 67
4 Andrea Dovizioso (Ita/Ducati) 66
5 Johann Zarco (Fra/Yamaha Tech3) 64
6 Danilo Petrucci (Ita/Ducati Pramac) 63
7 Andrea Iannone (Ita/Suzuki) 60
8 Cal Crutchlow (GB/LCR Honda) 56
9 Jack Miller (Aus/Ducati Pramac) 49
10 Jorge Lorenzo (Spa/Ducati) 41