A rotor (3, 3', 3'', 3''') for an aircraft (1) is described that comprises: a hub (5) rotatable about an axis (A) and, in turn, comprising a plurality of blades (9); a mast (6) connectable to a drive member of the aircraft (1) and connected to the hub (5) to drive the hub (5) in rotation about the axis (A); and damping means (15; 20a, 20b; 21a, 21b) to dampen the transmission of vibrations to the mast (6) in a plane orthogonal to the axis (A); the damping means (15; 20a, 20b; 21a, 21b) comprising at least a first mass (20a, 20b) and a second mass (21a, 21b) that can eccentrically rotate about the axis (A) with a first and a second speed of rotation ((N- 1)*Ω; -(N+1)*Ω), respectively; the first mass (20a, 20b) and second mass (21a, 21b) are operatively connected to the mast (6) to generate, respectively, a first and a second damping force on the mast (6) having a main component in a direction radial to the axis (A); the rotor (3, 3', 3'', 3''') comprises a transmission unit (19, 19', 19'', 19'''), which is interposed between the mast (6) and the first and second masses (20a, 20b; 21a, 21b) so as to drive the first and second masses in rotation (20a, 20b; 21a, 21b).