An injector for a fuel supply system of an internal combustion engine, namely for a common rail fuel supply system of an internal combustion engine which is formed in particular as a large diesel internal combustion engine or ship's diesel internal combustion engine, having an injection nozzle, a control valve and a retaining body. The injection nozzle and the control valve form a clamped composite, and the composite formed of the injection nozzle and control valve can be mounted on the retaining body as a unit and disassembled from the retaining body as a unit.