The invention relates to a cannula protector that serves to cover a cannula which has been attached to a syringe, particularly for the purpose of preventing unintended damage to the cannula as well as contamination of the cannula shortly before its use on the patient. The invention also relates to a single-use syringe system with such a cannula protector.A cannula protector according to these principles includes a tubular sleeve and a bellows which, in part together with the sleeve, completely encloses at least the area of the cannula. The cannula protector usually also comprises a radially acting clamp or engagement spring, whose function is to hold the inserted single-use syringe in the desired position, or to activate the protective mechanism.