The 1991 Vitesse du Mans motorcycle Grand Prix was a one-off race and the penultimate round of the 1991 Grand Prix motorcycle racing season.

It took place on the weekend of 6–8 September 1991 at the Bugatti Circuit located in Le Mans.

Originally meant to be held in Brazil, that race was cancelled for safety reasons, so the FIM decided to add a second French round.

It is the only time in FIM Grand Prix motorcycle racing history two rounds were held in France during a season.

Schwantz and Doohan battle for 1st, but at ten laps to go, Rainey just needs to stay in 3rd place to win the championship.