There is provided a motorcycle rear fender structure provided at a rear part of a motorcycle. A fender stay extends to an upper rear side from one side of left and right rear swing arms rotatably supporting a rear wheel. A rear fender main body covers an upper rear side of the rear wheel. A bulging portion bulges outward and rearward from the rear fender main body integrally. A wiring chamber is formed in the bulging portion. A partition wall is supported by the fender stay and provided in the rear fender main body. The partition wall is provided with a wiring hole for introducing an electrical wire connected to a lighting device into the wiring chamber. The fender stay is provided with a lower protruding portion extending in a left-right direction at a lower side of the wiring hole in the rear fender main body.