A developer supply container detachably mountable to an image forming apparatus, and includes a container body having a developer containing portion; a discharging opening, provided in the container body; a gas container storing a compressed gas; a plate-like member, disposed at a position between the container body and the gas container, and configured to move toward the discharge opening to discharge the developer in the developer containing portion through the discharge opening; a switch portion, operable from the image forming apparatus, configured and positioned to release the compressed gas from the gas container so that the plate-like member moves toward the discharge opening; and an urging portion configured and positioned to urge the switch portion to stop the release of the compressed gas from the gas container.