A fuel injector (1) comprising: an injection valve (7) provided with a mobile needle (15) to regulate the fuel flow; an actuator (6) adapted to shift the needle (15) an injection nozzle (3); a supporting body (4) having a tubular shape and displaying a feeding channel (5); a sealing body (17) provided with a valve seat (16) of injection valve (7) and comprising a disc-shaped capping element (18), which lowerly and fluid-tightly closes the feeding channel (5) and is crossed by the injection nozzle (3), and a guiding element (19), which rises from the capping element (18), has a tubular shape, and accommodates the needle (15) therein; an external fuel guiding channel (20) defined between the feeding channel (5) and the guiding element (19).