The 2021 FIM Motocross World Championship was the 65th FIM Motocross World Championship season.

The FIM Motocross World Championship is the premier championship of motocross racing, organized by the Fédération Internationale de Motocyclisme (FIM), divided into two distinct classes: MXGP and MX2. Race duration is 30 minutes plus two laps per race. The series runs 18 events with two races per class at each round. The FIM Women's Motocross World Championship (MXW) is a women-only motorcross championship, inaugurated in 2005, and is a feeder series to the FIM Motocross World Championship.