The invention relates to a flapping restrainer device for the blades of a rotorcraft main rotor, and a rotor head comprising the same. The lower restrainers comprise a reciprocal star-shaped plate (32), having as many radial branches (33) as blades, and each one of the branches being engaged into a radial opening (6) of the hub (3). Outside the latter, the star-shaped plate (32) cooperates with supporting runners (47) integral with the blades. The upper restrainers comprise, for each blade, a stop which is retractable by the effect of the centrifugal force and which is composed of a lever (52), pivoting on a pivot (53) carried by the hub (3), and a first arm (55) of which constitutes a stop finger directed towards an upper supporting component (60) integral with the blade, while a second arm (56) carries a governor weight (57) and a nose (58) for support against a shoulder (59) integral with the hub (3).