A helicopter comprising: - a fuselage with a nose; - a main rotor fitted to the top of said fuselage; and - an anti-torque rotor fitted to said fuselage on the opposite side of said nose; said anti-torque rotor comprising: - a supporting body; - a drive shaft which rotates about a first axis with respect to said supporting body; - a hub connected operatively to said drive shaft and angularly rotatable together with said drive shaft about said first axis; - at least one pair of blades which are connected operatively to said hub, are angularly rotatable together with said hub about said first axis, and are angularly rotatable about respective second axes and with respect to said hub to adjust the pitch angles of said blades; and - an actuator which can be operated to rotate said blades about said respective second axes to adjust the pitch angle of said blade; said actuator in turn comprising: - an electric motor which generates torque along said first axis; and - a mechanical stage interposed between said electric motor and said blades, and designed to convert said torque into rotation of said blades about the respective second axes; said electric motor being fixed to said supporting body; said mechanical stage comprising: - a rotary member which rotates about said first axis, and is rotated about said first axis by said electric motor; and - a sliding member which translates along said first axis, is fitted to said rotary member, and to which said at least two blades are hinged; said rotary member defining a first threaded surface, and said sliding member defining a second threaded surface which meshes with said first threaded surface; characterized in that said supporting body comprises: - a first body extending predominantly along a third axis crosswise to said first axis; - a second body connected to said first body and located on the opposite side of said first body with respect to said blades; and - a third body connected to said first body and located on the same side of said first body to said blades; said third body and second body being in the form of respective bells coaxial with said first axis and tapering towards said first axis, from said first body towards said blades, and from said first body away from said blades, respectively; said electric motor comprising: - a stator which is annular with respect to said first axis; - a rotor connected electrically to said stator and rotatable about said first axis by an electric torque generated by stator; and - a housing fixed to said second body and to which said stator is fixed; said electric motor being arranged outside said fuselage and external to said drive shaft, said blades and to said hub; said supporting body housing said electric motor, said first threaded surface and said second threaded surface. - a fuselage with a nose; - a main rotor fitted to the top of said fuselage; and - an anti-torque rotor fitted to said fuselage on the opposite side of said nose; - a supporting body; - a drive shaft which rotates about a first axis with respect to said supporting body; - a hub connected operatively to said drive shaft and angularly rotatable together with said drive shaft about said first axis; - at least one pair of blades which are connected operatively to said hub, are angularly rotatable together with said hub about said first axis, and are angularly rotatable about respective second axes and with respect to said hub to adjust the pitch angles of said blades; and - an actuator which can be operated to rotate said blades about said respective second axes to adjust the pitch angle of said blade; - an electric motor which generates torque along said first axis; and - a mechanical stage interposed between said electric motor and said blades, and designed to convert said torque into rotation of said blades about the respective second axes; - a rotary member which rotates about said first axis, and is rotated about said first axis by said electric motor; and - a sliding member which translates along said first axis, is fitted to said rotary member, and to which said at least two blades are hinged; - a first body extending predominantly along a third axis crosswise to said first axis; - a second body connected to said first body and located on the opposite side of said first body with respect to said blades; and - a third body connected to said first body and located on the same side of said first body to said blades; - a stator which is annular with respect to said first axis; - a rotor connected electrically to said stator and rotatable about said first axis by an electric torque generated by stator; and - a housing fixed to said second body and to which said stator is fixed;