An injector for a system for feeding gas fuel to an internal combustion engine, comprising: - a casing having at least one inlet mouth for the fuel and at least one outlet mouth selectively traversable by the fuel coming from the inlet mouth and fluidically connectable to a cylinder of the engine; - an anchor housed inside the casing between the inlet and outlet mouths and comprising a shutter adapted to cooperate selectively with one of said inlet and outlet mouths to prevent the fluidic connection between the same; - elastic means acting on a first portion of the anchor spaced from the shutter; and - an electromagnet selectively activated to generate a magnetic field on the anchor opposite to the force generated by the elastic means on the anchor itself; said electromagnet comprising a core made of magnetic material and a coil wound on the core and powered electrically in a selective manner; said anchor being movable between a first operative configuration, in which the shutter engages said one of said inlet and outlet mouths to prevent delivery of the fuel to the cylinder, and a second operative configuration, in which the shutter leaves open said one of said inlet and outlet mouths so as to allow delivery of the fuel inside the cylinder; said elastic means cooperating with the anchor to keep the same in one of said first and second operative configuration and said electromagnet being selectively activated to generate a force of attraction on said anchor and move the same in another of said first and second operative configurations against the action of the elastic means; characterized by further comprising: - positioning means (31, 39) of the anchor inside the casing defining, in said other of said first and second operative configurations, an air gap between the core and a second portion of said anchor facing the core itself and distinct from said first portion; and- a magnetic flux conveying element, in particular made of a ferrous material with low carbon content, interposed between the core and the anchor; said positioning means comprising at least one spacer interposed between the magnetic flux conveying element and the anchor, in a remote position with respect to said second portion; said spacer being configured to maintain an air gap between the anchor and the magnetic flux conveying element with the exception of the action area of the spacer itself; said magnetic flux conveying element being fixed inside the casing in a position in which it is separated from the core by means of an air gap. - a casing having at least one inlet mouth for the fuel and at least one outlet mouth selectively traversable by the fuel coming from the inlet mouth and fluidically connectable to a cylinder of the engine; - an anchor housed inside the casing between the inlet and outlet mouths and comprising a shutter adapted to cooperate selectively with one of said inlet and outlet mouths to prevent the fluidic connection between the same; - elastic means acting on a first portion of the anchor spaced from the shutter; and - an electromagnet selectively activated to generate a magnetic field on the anchor opposite to the force generated by the elastic means on the anchor itself; said electromagnet comprising a core made of magnetic material and a coil wound on the core and powered electrically in a selective manner; said anchor being movable between a first operative configuration, in which the shutter engages said one of said inlet and outlet mouths to prevent delivery of the fuel to the cylinder, and a second operative configuration, in which the shutter leaves open said one of said inlet and outlet mouths so as to allow delivery of the fuel inside the cylinder; said elastic means cooperating with the anchor to keep the same in one of said first and second operative configuration and said electromagnet being selectively activated to generate a force of attraction on said anchor and move the same in another of said first and second operative configurations against the action of the elastic means; - positioning means (31, 39) of the anchor inside the casing defining, in said other of said first and second operative configurations, an air gap between the core and a second portion of said anchor facing the core itself and distinct from said first portion; and- a magnetic flux conveying element, in particular made of a ferrous material with low carbon content, interposed between the core and the anchor; said positioning means comprising at least one spacer interposed between the magnetic flux conveying element and the anchor, in a remote position with respect to said second portion; said spacer being configured to maintain an air gap between the anchor and the magnetic flux conveying element with the exception of the action area of the spacer itself; said magnetic flux conveying element being fixed inside the casing in a position in which it is separated from the core by means of an air gap.