Actuation device for actuating a hydraulic actuator such as a brake and/or clutch, in particular for motorcycles, the device comprising: - a support suitable for being connected to a weight-bearing structure, - a hydraulic actuator connected to the support, - at least one lever device connected to the support so as to rotate around an actuation axis (R-R) so as to permit its movement towards and/or away from the hydraulic actuator to influence said hydraulic actuator in movement, a command rod and an adjustment device positioned between the at least one lever device and a piston of said hydraulic actuator so as to transmit the movement from the at least one lever device to said piston, wherein the adjustment device is supported so as to rotate around an adjustment axis (X-X) and comprises a first end which interfaces, at least partially by means of a shaped coupling, with an end of the command rod, - wherein said first end of the adjustment device is eccentric to the adjustment axis (X-X) so that a rotation of the adjustment device is adapted to produce a variation/adjustment of the orientation of the command rod in relation to the actuation axis (R-R) of the at least one lever device and thereby the adjustment of the lever ratio, - wherein the at least one lever device comprises a clamp connected to the support so as to rotate around said actuation axis (R-R) and an actuation lever, suitable for being gripped by the user, wherein a first regulator is inserted between the at least one lever device and the adjustment device which is adapted to regulate the axial position of the adjustment device in relation to the at least one lever device, said position being measured parallel to the adjustment axis (X-X), the first regulator being axially constrained to the adjustment device so as to translate with it parallel to the adjustment axis (X-X) along an adjustment stroke (δ), characterised in that the first regulator is a bush screwed into a threaded seat made on said clamp, said bush being hollow so as to house the adjustment device at least partially, the adjustment device being joined to the first regulator by means of a coupling which axially joins the adjustment device and the first regulator to each other parallel to the adjustment axis (X-X) and which permits the relative rotation between them in relation to said adjustment axis (X-X). - a support suitable for being connected to a weight-bearing structure, - a hydraulic actuator connected to the support, - at least one lever device connected to the support so as to rotate around an actuation axis (R-R) so as to permit its movement towards and/or away from the hydraulic actuator to influence said hydraulic actuator in movement, - wherein said first end of the adjustment device is eccentric to the adjustment axis (X-X) so that a rotation of the adjustment device is adapted to produce a variation/adjustment of the orientation of the command rod in relation to the actuation axis (R-R) of the at least one lever device and thereby the adjustment of the lever ratio, - wherein the at least one lever device comprises a clamp connected to the support so as to rotate around said actuation axis (R-R) and an actuation lever, suitable for being gripped by the user,