A developer supply system including a developer supply apparatus and a developer supply container which is detachably mountable to the apparatus, the system includes the developer supply container including a rotatable container body having an inner space configured and positioned to contain a developer; a feeding portion configured and positioned to feed the developer in the container body to discharge the developer out of the container body with a rotation of the container body; and a hooking portion configured and positioned to engage with the apparatus to receive a rotational force for rotating the container body; the apparatus including a driving member configured and positioned to apply the rotational force; a drive transmitting member configured and positioned to engage with the hooking portion to transmit the rotational force from the driving member to the hooking portion, the drive transmitting member, which has engaged with the hooking portion, being movable between a first position where the drive transmitting member and the driving member are engaged with each other and a second position where the drive transmitting member and the driving member are not engaged with each other; and a displacing member configured and positioned to displace the hooking portion to release an engagement between the hooking portion and the drive transmitting member which is in the second position.