The California Highway Patrol says it happened just before noon near Auberry and Millerton Roads in Fresno County.
They say the bicyclist was going southbound on Auberry and the 39-year-old motorcyclist was going the same direction.
Officials say the bicyclist went onto the roadway for an unknown reason and was hit by the motorcyclist.
Attempts were made to revive the 72-year-old, but he ultimately died at the scene. The motorcyclist suffered injuries to his arm.
Authorities added that alcohol or drugs did not play a role in this collision.