An internal combustion engine for a motor-vehicle comprising: - at least one cylinder having a longitudinal axis and adapted to receive fuel and air for carrying out an engine cycle including a combustion reaction of the fuel itself; - at least one intake duct adapted to feed said cylinder with fresh air, through at least one intake port; - at least one intake valve acting on said intake port for controlling the airflow entering said cylinder; - at least one injector that can be selectively activated to supply uncombusted fuel to said cylinder; - at least one exhaust duct communicating with said cylinder through at least one outlet port for removing from the cylinder exhaust gases formed at the end of said combustion; - at least one outlet valve acting on said outlet port for controlling the flow of the exhaust gases at the outlet of said cylinder; and - a piston mounted in a linearly sliding manner along said longitudinal axis within said cylinder; wherein said intake port, said outlet port and said injector are carried by a head of the engine, said head being arranged in abutment against an axial end of said cylinder and delimiting with said piston and with the cylinder a combustion chamber; said engine further comprising: - at least a first spark plug mounted on said head and acting inside said combustion chamber for cyclically and selectively determining the ignition of the mixture formed by fuel and air present in the combustion chamber and for triggering the combustion reaction; - a pre-chamber, delimited towards said combustion chamber by a wall, communicating with the combustion chamber through one or more free connection ports and fed with a mixture of air and fuel, and - a second spark plug acting inside said pre-chamber for cyclically and selectively determining the ignition of the mixture present in the pre-chamber and triggering the combustion reaction; - said first spark plug being arranged in an intermediate position between said pre-chamber and said injector; characterized in that - said first spark plug is in a position adjacent to said injector, and - said pre-chamber is arranged in a central position inside said combustion chamber. - at least one cylinder having a longitudinal axis and adapted to receive fuel and air for carrying out an engine cycle including a combustion reaction of the fuel itself; - at least one intake duct adapted to feed said cylinder with fresh air, through at least one intake port; - at least one intake valve acting on said intake port for controlling the airflow entering said cylinder; - at least one injector that can be selectively activated to supply uncombusted fuel to said cylinder; - at least one exhaust duct communicating with said cylinder through at least one outlet port for removing from the cylinder exhaust gases formed at the end of said combustion; - at least one outlet valve acting on said outlet port for controlling the flow of the exhaust gases at the outlet of said cylinder; and - a piston mounted in a linearly sliding manner along said longitudinal axis within said cylinder; - at least a first spark plug mounted on said head and acting inside said combustion chamber for cyclically and selectively determining the ignition of the mixture formed by fuel and air present in the combustion chamber and for triggering the combustion reaction; - a pre-chamber, delimited towards said combustion chamber by a wall, communicating with the combustion chamber through one or more free connection ports and fed with a mixture of air and fuel, and - a second spark plug acting inside said pre-chamber for cyclically and selectively determining the ignition of the mixture present in the pre-chamber and triggering the combustion reaction; - said first spark plug being arranged in an intermediate position between said pre-chamber and said injector; - said first spark plug is in a position adjacent to said injector, and - said pre-chamber is arranged in a central position inside said combustion chamber.