A removable heating device for a hot runner nozzle contains an elongated heating unit which exhibits at least one longitudinal slot which does not extend as far in the longitudinal direction as the length of a substantially cylindrical heating unit and which enables an enlargement of the inner diameter of the heating unit by its open end. The heating device further has a channel disposed in the outer surface of the heating unit in which an electrical heating element is disposed. Furthermore, a heater/thermocouple assembly contains such a heating device and at least one thermocouple for detecting the temperature in the front end region of the hot runner nozzle.