A toner supply container is detachably mountable to an image forming
apparatus and includes: a container body for accommodating toner; an
opening, formed in the container body, for permitting the supply of the
toner into the image forming apparatus; and a driving-force receiving
member for receiving a driving-force from a driving-force applying member
provided in the main assembly. The driving-force receiving member
includes an elastic press-fitting engagement member which is engageable
with an elastic press-fitting engagement member provided in the main
assembly. A part of one of the elastic press-fitting engagement members
which is an elastic member is elastically restorable to establish
driving-force transmitting engagement between the two engagement members.