The championship was contested over eighteen rounds. The 2021 season saw the debut of Beta as a manufacturer in the MXGP class. In MX2, Tom Vialle was the defending champion as he picked up his maiden world title in the previous year.
In the MXGP class, Tim Gajser started the season as the reigning champion after picking up his fourth world title in 2020. The 2021 FIM Motocross World Championship was the 65th FIM Motocross World Championship season.