The 1985 Grand Prix motorcycle racing season was the 37th Road Racing World Championship season.
Honda's Freddie Spencer gave a dominating performance becoming the first man to win the 250 and 500 championships in the same year. Defending champion Eddie Lawson finished in second with former 250 world champion, Christian Sarron coming in third. Sarron's victory at the German Grand Prix would mark the first 500cc Grand Prix victory for a non-American rider since the 1982 Swedish Grand Prix. Australian Wayne Gardner showed promise with a fourth-place finish for Honda.
With perennial champion Angel Nieto moving to the 80cc class, the 125 class was left open for his Garelli team-mate, Fausto Gresini to clinch the title, giving the Italian team its fourth consecutive championship. Swiss Stefan Dörflinger would take his fourth consecutive title in the 80cc class. Angel Nieto won his 90th and final Grand Prix victory in the 80cc round in France, at the time second only to Giacomo Agostini, but since surpassed by Valentino Rossi.