Abstract: A lawn mower includes a cutting unit having two rotors coupled together within a single casing which rotate in opposite directions. The rotors carry at least two aligned blades. The distance between the axes of the rotors is such that the areas covered by the blades when rotating are partially superposed in correspondence with an axis of symmetry of the pair of rotors which coincides with the mower axis. The direction of rotation of the two rotors is such that the direction of movement of the blades when in proximity to said axis of symmetry is the same as the forward travel direction of the mower.