An electrophotographic photosensitive drum for a process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus for forming an image on a recording material, said main assembly including a motor, a main assembly gear for transmitting a driving force from said motor, and a non-circular twisted hole having a section with a plurality of corner portions provided at a central portion of the main assembly gear, said non-circular twisted hole being rotatable integrally with the main assembly gear, said electrophotographic photosensitive drum comprising: (a) a cylinder having a photosensitive layer on a peripheral surface thereof; (b) a flange attached to one longitudinal end of said cylinder; (c) a shaft portion, for rotatably supporting of said electrophotographic photosensitive drum, provided on said flange and located at the outward end of said flange; (d) a non-circular twisted projection provided on said shaft portion and having a section with a plurality of corner portions, said non-circular twisted projection being engageable with the hole of the main assembly of the apparatus to receive transmission of a driving force from the main assembly of the apparatus when said process cartridge is mounted to the main assembly of the apparatus; characterized by a cylindrical recess formed in a central portion of said projection whereby an axial line of said recess coincides with an axial line of said electrophotographic photosensitive drum, wherein said recess has a bottom surface and a side surface which are formed as a supporting and centering portion for supporting and centering a spherical surface portion, provided at a central portion of the hole, of the main assembly of the apparatus, and wherein when said projection receives a pulling force toward said hole by rotation of the main assembly gear with the projection and the hole being engaged with each other, said bottom surface is contacted to said spherical surface portion provided at the central portion of said hole and said side surface is contacted to said spherical surface portion whereby the axial line of said electrophotographic photosensitive drum and an axial line of the hole are in alignment with each other; wherein, when said process cartridge is mounted to the main assembly of said apparatus and said electrophotographic photosensitive drum receives a driving force for rotation from the main assembly of the apparatus, an end (70a2) of said spherical surface portion is contacted to said bottom surface, said spherical surface portion is contacted to said side surface in a state that said projection receives the pulling force, and a gap is provided between a free end (61b1) of said projection and a bottom portion (70a1) of the hole. (a) a cylinder having a photosensitive layer on a peripheral surface thereof; (b) a flange attached to one longitudinal end of said cylinder; (c) a shaft portion, for rotatably supporting of said electrophotographic photosensitive drum, provided on said flange and located at the outward end of said flange; (d) a non-circular twisted projection provided on said shaft portion and having a section with a plurality of corner portions, said non-circular twisted projection being engageable with the hole of the main assembly of the apparatus to receive transmission of a driving force from the main assembly of the apparatus when said process cartridge is mounted to the main assembly of the apparatus;