Martin grabbed the holeshot off the line from third on the grid and led all 25 laps to secure his first grand prix victory of the season.
Behind Martin drama unfolded as Ducati’s Enea Bastianini took second from Aprilia’s Maverick Vinales in a bizarre incident on the penultimate lap.
Vinales slowed on the pit straight and allowed Bastianini to come through, before the Aprilia rider and sprint winner ran off at Turn 1 and crashed on the dusty run-off area.
This released a stunning Pedro Acosta into third, after the Tech3 GasGas rookie battled his way through from seventh on the grid to secure a maiden MotoGP podium in just his second grand prix.
A lap prior to this moment, Marquez and Bagnaia collided at Turn 5 as the former attempted an overtake for fifth.
Gresini’s Marquez launched a rain on the inside of Bagnaia into the Turn 5 right-hander, but ran slightly wide as he did so.
Cutting back to try to defend the line, the pair collided. Both were able to remount, but Bagnaia retired into the pits while Marquez finished 16th.
The incident will be reviewed by the stewards after the race.
Francesco Bagnaia, Ducati Team
Photo by: Gold and Goose / Motorsport Images
Pramac’s Martin, Vinales and Bastianini quickly emerged as the breakaway group in the grand prix as Bagnaia slotted into fourth on the opening lap.
Marquez from eighth on the grid came close to tagging Bagnaia at Turn 5 on the opening lap as they battled with KTM’s Jack Miller.
Both Bagnaia and Marquez were able to jump Miller, who eventually fell into the clutches of KTM team-mate Brad Binder and Tech3’s Acosta.
Acosta would work his way into sixth ahead of Binder on lap seven of 25, before taking fifth from Marquez next time around.
The rookie shadowed Bagnaia, whose pace couldn’t match the leaders, until lap 21 when he made a successful pass for fourth after several prior attempts.
Marquez, who looked like he’d dropped out of the battle for fourth in the closing stages, rallied after Acosta moved ahead of Bagnaia and came close on lap 22 to overhaul the factory Ducati.
On lap 23, Marquez made another attempt on Bagnaia before it ended in disaster, promoting the factory KTM duo of Binder and Miller into the top five.
At the front of the field, Martin extended his lead to over a second at the halfway mark and kept it stable despite late fastest lap efforts from Vinales and Bastianini.
As Martin began his final lap, Bastianini eased past Vinales as the Aprilia suddenly slowed onto the pit straight.
Aprilia says Vinales’ bike suffered a suspected gearbox issue, which caused him to slow onto the final lap before ultimately crashing.
Bastianini was already well ahead when Vinales crashed on the run-off area at Turn 1, which promoted Acosta to third.
Martin took the checked flag 0.882s clear of Bastianini, with Acosta 4.480s behind in third.
Binder was five seconds clear of Miller at the finish, with Marco Bezzecchi sixth on his VR46 Ducati ahead of Yamaha’s Fabio Quartararo and Aprilia’s Aleix Espargaro.
Home hero Miguel Oliveira was ninth on the Trackhouse Racing Aprilia, with Fabio Di Giannantonio 10th on the second VR46 bike.
Augusto Fernandez was 11th on the second Tech3 GasGas, with Honda’s Joan Mir, Yamaha’s Alex Rins, Takaaki Nakagami (LCR) and Johann Zarco (LCR) taking the final points.
Alex Marquez (Gresini) and Raul Fernandez (Trackhouse) crashed out early on, while Franco Morbidelli (Pramac) was 18th after suffering a fall on lap one.
Martin now leads the championship by 18 points from Binder, with Bagnaia 23 adrift after his DNF.