The 1965 Grand Prix motorcycle racing season was the 17th F.I.M. Road Racing World Championship Grand Prix season. The season consisted of thirteen Grand Prix races in six classes: 500cc, 350cc, 250cc, 125cc, 50cc and Sidecars 500cc. It began on 21 March, with United States Grand Prix and ended with Japanese Grand Prix on October, 24.

Mike Hailwood easily claimed his fourth successive 500 class crown for MV Agusta, although he was beginning to show his disenchantment with the autocratic Count Agusta by accepting a 250 class ride from Honda.^[1] Newcomer Giacomo Agostini riding for MV Agusta would battle Honda's reigning champion Jim Redman for the 350 title.^[1] The outcome wouldn't be decided until the final race of the year in Japan, when Agostini's MV Agusta suffered a mechanical failure, handing the championship to Redman.^[1]

The Yamaha duo of Phil Read and Michelle Duff finished first and second in the 250 class, as Honda's Redman battled early season injuries.^[1] Hugh Anderson won six races to claim his second 125 championship for Suzuki while Honda's Ralph Bryans took the 50cc crown ahead of his Honda teammate Luigi Taveri.^[1]