Abstract: A fuel injector for internal combustion engines, the injector a nozzle needle axially guided for movement in a nozzle body to opens or close off at least one spray hole for a fuel injection, having a valve piston is guided so as to be axially moveable in a holding body and controls the opening and closing movement of the nozzle needle, having a valve piece in which the valve piston delimits a control space which is connected to a high-pressure side and which is connected by means of a control valve to a low-pressure side, and having a leakage oil return line which discharges leakage oil out of the region of the holding body. The leakage oil return line runs at least partially in the valve piece.