The 2018 FIM MotoGP World Championship was the premier class of the 70th Fédération Internationale de Motocyclisme (FIM) Road Racing World Championship season, the highest level of competition in motorcycle road racing. Marc Márquez entered the season as the reigning champion, with Repsol Honda Team being the reigning team champions and Honda the reigning constructors' champions.

Originally scheduled for 19 races, the season was reduced by one Grand Prix due to the cancellation of the 26 August Silverstone event due to unsafe track conditions involving standing water after a rider vote.

Marc Márquez clinched the championship trophy on 21 October 2018 after sixteen rounds, winning three consecutive races during spring, another three consecutive races during autumn and nine overall. Andrea Dovizioso finished in second and Valentino Rossi ended up in third, the former with four wins, while Rossi did not record a race win. Jorge Lorenzo with three wins and a win apiece for Cal Crutchlow and Maverick Viñales were the other race winners. Yamaha suffered their worst winless streak in their history with no wins for 25 races, which lasted from the 2017 German Grand Prix until Viñales won the Australian Grand Prix. KTM got their first podium finish at the Valencian Grand Prix with Pol Espargaró, finishing in third.

All teams used series-specified Michelin tyres.

The following Grands Prix took place in 2018:

Points were awarded to the top fifteen finishers. A rider had to finish the race to earn points.

Each constructor received the same number of points as their best placed rider in each race.

The teams' standings were based on results obtained by regular and substitute riders; wild-card entries were ineligible.