A toner cartridge is provided, which comprises a toner bottle containing toner, and a support member supporting the toner bottle in an axially rotatable manner. The toner bottle has a toner outlet port provided in a portion thereof supported by the support member. The support member has an outlet port shutter provided slidably on an outer surface thereof for opening and closing the toner outlet port, and a projecting engagement portion for positioning the toner cartridge with respect to a cartridge insertion port of an image forming apparatus when the toner cartridge is mounted in the image forming apparatus. The support member and the toner bottle respectively have a projection and a recess serving as a locking portion and a to-be-locked portion for restricting rotation of the toner bottle with respect to the support member when the toner cartridge is not mounted in the image forming apparatus.