The invention relates to a fuel injector (1) for internal combustion engines, the injector includes a nozzle needle (5) axially guided for movement in a nozzle body(4) to opens or close off at least one spray hole (9) for a fuel injection, having a valve piston (12) is guided so as to be axially moveable in a holding body and controls the opening and closing movement of the nozzle needle (5), having a valve piece (16) in which the valve piston (12) delimits a control space (17) which is connected to a high-pressure side (2) and which is connected by means of a control valve to a low-pressure side (22), and having a leakage oil return line (23; 23') which discharges leakage oil out of the region of a holding body (14). The leakage oil return line (23; 23') runs at least partially in the valve piece (26).