The 21-year-old Spaniard saw off the challenge of Andrea Dovizioso to become the first rider since Giacomo Agostini in 1971 to have won the opening eight rounds.
With the track drying after rain, tire choices proved a crucial factor and Marquez began with intermediates but then changed to a dry kit early on, as did Dovizioso.
The pair swept past Aleix Espargaro, who had started the race in pole but suffered a spill to blow his chances.
A rare Marquez steering mistake then saw Dovizioso take the lead, but the young Spanish rider???s Honda had better speed and he retook the lead with 11 laps to go and was never headed.
Dovizioso eventually came home 6.74 seconds behind, with Marquez’s Repsol Honda teammate Dani Pedrosa back in third. ????