A fuel injector (1) for fuel injector systems of internal combustion engines has a valve-closure member (4) which is mechanically linked to a valve needle (3) and cooperates with a valve-seat surface (6) of a valve-seat member (5) to form a sealing seat. A turbulence-producing element is provided in the valve-seat member (5), situated downstream from the sealing seat, and its center line (38) preferably forms an angle different from zero with the center line (39) of the fuel injector (1), a threaded rod (36) being pressed into the valve-seat member (5) as the turbulence-producing element.