An electrophotographic photosensitive drum includes a non-circular twisted projection, provided at one longitudinal end of the drum, having a cross-section with a plurality of corner portions, and being engageable with a non-circular twisted hole located at a central portion of a driving rotatable member of a main assembly of an image forming apparatus and has a cross-section with a plurality of corner portions; and a second electroconductive member contactable with a first electroconductive member electrically connected with the main assembly of the image forming apparatus. The first electroconductive member is disposed in the hole to ground the drum. The second electroconductive member is provided on the projection and electrically connected with the drum. The contact position between the first and second electroconductive members moves in interrelation with the projection being retracted toward the hole by rotation of the driving rotatable member when the projection is engaged with the hole.