A storage bin that is assembled at the rear of a motor vehicle includes a molded part made from polymer material defining, in the mounted position of the bin: an upper supporting rim, a bin bottom situated below the upper supporting rim, and one or more sidewall portions. The molded part further includes two oblique rims extending between the upper supporting rim and the bin bottom. The molded part is traversed by a lateral opening forming a notch from above, the notch being bordered by the two oblique or vertical rims. The lateral opening is closed by an attached wall assembled to the two oblique or vertical rims.