An image forming apparatus includes a main assembly, a cartridge, a rotationally movable member, an engaging portion, and a flexible member integrally including a first supported portion, a second supported portion, and a regulating portion. A position of the regulating portion of the flexible member relative to the engaging portion is changeable by a change in a flexed state of a portion of the flexible member between the first supported portion and the second supported portion, in interrelation with a change in relative position between the first supported portion and the second supported portion with rotational movement of the rotationally movable member When the rotationally movable member is in the first position, the regulating portion is in a regulating position to limit the elastic deformation of the engaging portion.