Fuel injector arranged to deliver high-pressure fuel to an internal combustion engine via injection holes , the injector comprising: an injector body extending along a longitudinal axis (X) comprising a bore and a high-pressure chamber , and a needle arranged so as to slide in the bore between an upper guide and a lower guide , the needle extending between a first end provided with a valve obturator and a second end provided with an open bore , the needle being able to move between an open position and a closed position, a piston comprising a magnetic armature and a shaft extending along a longitudinal axis (X) between a first end and a remote second end secured to the magnetic armature , an actuator comprising a fixed solenoid and generating, when supplied with electricity, and opening force on the magnetic armature and, a return spring generating a closing force on the piston when the solenoid is not energized, characterized in that the injector further comprises a high-pressure duct extending between an inlet mouth of the injector and the injection holes , the high-pressure duct comprising a first segment extending in the needle , a second segment extending in the shaft and a third segment extending in the armature and, in that the first end of the shaft is guided in the bore of the needle and, in that the injector further comprises a force amplifier arranged between the shaft and the needle , the piston moving under the action of an electromagnetic force (F1) generated by the solenoid as well as under the action of a force (F2) generated by the return spring such that the resultant force (Fr) acting on the piston is transmitted to and amplified at the needle , the force amplifier comprising a hydraulic amplification chamber defined in part by an annular shoulder of the shaft of the piston and by a thrust face of the second end of the needle, said thrust face having a surface area (A62) greater than the surface area (A60) of the shoulder. an injector body extending along a longitudinal axis (X) comprising a bore and a high-pressure chamber , and a needle arranged so as to slide in the bore between an upper guide and a lower guide , the needle extending between a first end provided with a valve obturator and a second end provided with an open bore , the needle being able to move between an open position and a closed position, a piston comprising a magnetic armature and a shaft extending along a longitudinal axis (X) between a first end and a remote second end secured to the magnetic armature , an actuator comprising a fixed solenoid and generating, when supplied with electricity, and opening force on the magnetic armature and, a return spring generating a closing force on the piston when the solenoid is not energized, characterized in that the injector further comprises a high-pressure duct extending between an inlet mouth of the injector and the injection holes , the high-pressure duct comprising a first segment extending in the needle , a second segment extending in the shaft and a third segment extending in the armature and, in that the first end of the shaft is guided in the bore of the needle and, in that the injector further comprises a force amplifier arranged between the shaft and the needle , the piston moving under the action of an electromagnetic force (F1) generated by the solenoid as well as under the action of a force (F2) generated by the return spring such that the resultant force (Fr) acting on the piston is transmitted to and amplified at the needle , the force amplifier comprising a hydraulic amplification chamber defined in part by an annular shoulder of the shaft of the piston and by a thrust face of the second end of the needle, said thrust face having a surface area (A62) greater than the surface area (A60) of the shoulder. <EOS>