Andrea Dovizioso stormed to MotoGP victory in Misano ahead of Marc Marquez, while Jorge Lorenzo crashed out of second late on.
Lorenzo nailed his launch from pole position to take the lead into Turn 1 ahead of Ducati stablemate Jack Miller on the Pramac GP17, with Honda man Marquez third.
With Lorenzo already trying to break away, team-mate Dovizioso wasted no time in dispatching Marquez and Miller across the opening lap, and shadowed the race leader by the start of lap three.
Marquez barged past Miller at Carro on the second tour, and edged his way towards the top two, who had swapped position on lap six.
By lap 10, Dovizioso had built up an advantage of 0.7s, which he soon extended to over a second, while Marquez passed Lorenzo at Carro on the 14th tour.
The future Honda team-mates engaged in in battle over the next few laps, with Lorenzo getting the upper hand with a daring move on Marquez on the inside of Turn 12.
Dovizioso held a 2.5s lead at this point, but the chasing Lorenzo and Marquez were able to reduce that by a second with three laps remaining.
Pushing to further reduce that gap and put pressure on his team-mate, Lorenzo crashed at Quercia on the penultimate tour, allowing Dovizioso to ease to his third win of the season and the first for Ducati at Misano in 11 years.
Lorenzo's demise gifted second to Marquez, who now holds a 67-point lead over Dovizioso in the championship standings.
LCR's Cal Crutchlow closed down the warring Lorenzo and Dovizioso in the second half of the race, and crossed the line to complete the podium for the second time this season.
Suzuki's Alex Rins gambled on running the soft rear tyre despite the high temperatures, and was fourth ahead of Maverick Vinales, whose fifth sees Yamaha's losing streak in MotoGP extend to 22 races.
Team-mate Valentino Rossi was a lowly seventh in front of his home fans, with Dani Pedrosa splitting the factory M1s. Andrea Iannone, Alvaro Bautista and Johann Zarco – who also ran the soft rear tyre – completed the top 10.
Danilo Petrucci recovered from stalling on the grid on the warm-up lap to finish 11th despite a 1.1s time penalty for a track limits infringement, while Franco Morbidelli, Takaaki Nakagami, Aleix Espargaro and wildcard Michele Pirro took the final points.
Lorenzo rejoined after his late fall, and shadowed KTM's Bradley Smith across the line in 17th, with Miller – who fell on the third lap – following his Ducati stablemate in 18th.
HRC wildcard Stefan Bradl crashed out late on, with Avintia's Xavier Simeon falling off early on. Pol Espargaro retired his KTM due to ongoing injury issues.
