1981 FIM Motocross World Championship

The reigning 500cc World Champion André Malherbe (Honda) successfully defended his title after a season-long battle with his Honda teammate Graham Noyce who had missed most of the 1980 season after sustaining a broken leg. As in 1980, the championship wasn't decided until the final race in Luxembourg where Malherbe would prevail to score his second consecutive World Championship.^[1][2][3]

Malherbe began the year by winning the 500cc Austrian Grand Prix but then suffered a dislocated shoulder at the second round in Switzerland. He also experienced mechanical problems Sweden, France, and Great Britain which allowed Noyce to take the championship points lead at mid-season.^[4] Malherbe then reclaimed the championship points lead at his home Grand Prix in Belgium when Noyce withdrew with a mechanical failure. Noyce was 10 points behind Malherbe with one race left in the season however, Malherbe clinched the World Championship when he finished in second place behind Håkan Carlqvist (Yamaha) at the season-ending 500cc Luxembourg Grand Prix.

Carlqvist took third place in the championship with six podium results in the final six races of the season, including victories in the final two races of the year.^[4] Suzuki returned to Grand Prix motocross after a three-year hiatus and hired Brad Lackey, the 1980 500cc class runner-up. Lackey struggled with injuries and mechanical problems while developing a new motorcycle and dropped to sixth in the 1981 world championship.^[5] Future three-time World Champion David Thorpe competed in his first Motocross World Championship event at the 1981 500cc French Grand Prix riding for the Kawasaki-UK team.^[4]

Georges Jobé (Suzuki) won five of the first seven Grand Prix races to lead the 1981 250cc Motocross World Championship by 53 points over his closest rival, Neil Hudson (Yamaha) with four rounds remaining and appeared to be heading towards a second consecutive World Championship when he was injured while competing in a Belgian National Championship race.^[6] He attempted to compete in the penultimate round in Russia but was injured again, allowing Hudson to overtake him and win the World Championship by only two points in the final standings.^[6][7]

The 1981 125cc Motocross World Championship developed into a four-way battle between the defending champion Harry Everts (Suzuki), Michele Rinaldi (Gilera), Eric Geboers (Suzuki), and Marc Velkeneers (Yamaha). After the first ten rounds of the championship the four competitors were 12 points apart but, Everts won the last two Grand Prix races of the year to claim his third consecutive 125cc Motocross World Championship ahead of his Suzuki teammate, Geboers.^[8]