Abstract: A fuel injector is disclosed for high atomization capacity, and is of the single-jet air-assisted type in which a stop valve moved by an electromagnetic actuator controls the formation of fuel jets through atomization holes contained in a distributor element after which there is disposed an auxiliary atomization chamber. The auxiliary atomization chamber is delimited internally at least partially by a truncated conical surface onto which there opens substantially radial holes for the provision of auxiliary air, the truncated conical surface being defined by a mixer element disposed with a seal between the distributor element and a cap which is snap-fitted to a casing of the fuel injector.