Cartridge and image forming apparatus

A cartridge attachable to an apparatus main body of an image forming apparatus, the apparatus main body having a restricting portion and to which the cartridge is mounted by being moved from a unmounted position to a mounting-completed position in a first direction, the cartridge includes a developer container provided with a supply port, and a shutter movable between an opening position for opening the supply port and a closing position for closing the supply port, having a restricted portion, and configured to be in the closing position when the cartridge is in the unmounted position and be in the opening position when the cartridge is in the mounting-completed position, wherein a movement of the shutter in a second direction perpendicular to the first direction is restricted by an engagement between the restricting portion and the restricted portion when the cartridge is in the mounting-completed position.