A fuel injector for fuel injection systems of internal combustion engines, in particular for direct injection of fuel into the combustion chamber of an engine, including an actuator, a valve needle which is mechanically linked to the actuator and is acted upon by a restoring spring in a closing direction, for actuation of a valve closing body, which together with a valve seat face forms a sealing seat, and including a sleeve which pre-stresses the restoring spring. An adjusting body is situated adjustably in the sleeve so that a fuel amount flowing through the fuel injector per unit of time is a function of the position of the adjusting body in the sleeve.