FIM Endurance world champion Anthony Delhalle was killed in an accident during testing at the Nogaro circuit in France.
Suzuki rider Delhalle, 35, crashed at the end of the pit straight during the first test session, run in preparation for the 24 Heures Motos event on Thursday morning.
Delhalle, married and with two children, received medical attention straight away but did not survive the injuries.
"Anthony came out straight, without reason or loss of grip," explained his teammate Vincent Philippe. "It's incredible and inexplicable. I feel like a part of me has gone."
Frenchman Delhalle helped the Suzuki Endurance Racing Team to the FIM EWC teams' title last year, racing alongside compatriots Philippe and Etienne Masson.