A developer supply container supplies a developer to a process cartridge detachably mounted to an electrophotographic image forming apparatus. The process cartridge contains an electrophotographic photosensitive drum and a charging member for charging the drum. The developer supply container includes a developer accommodating portion, a developer supply opening for supplying the developer accommodated in the developer accommodating portion to the cartridge, a container closing member for opening and closing the developer supply opening, a first container guide guidable by an apparatus main assembly guide, a second container guide guidable by the main assembly guide, a container force receiving portion for receiving a force for opening the supply opening by movement of the closing member by engagement with a cartridge engaging portion provided in the cartridge, and a first container positioning portion engageable with a first main assembly positioning portion.