Abstract: The tire filling unit, particularly for filling a bicycle tire, comprises a filling head with an outlet connectable to a filling valve of a tire and with an inlet containing a hollow prong for a high pressure gas cartridge and a concentric cartridge jacket attachable with the filling head at the inlet for receiving the high pressure cartridge. A connecting duct contains an automatically closing valve between the inlet and the outlet which locks the connecting duct in a closed configuration and which is movable into an open configuration by an operating device mounted in the filling head.