A hydraulically operated disk brake including a hydraulically actuated parking brake which includes: - a brake calliper which includes a housing wherein at least one primary hydraulic cavity is formed which is axially open toward the front and defined axially toward the rear by a transverse back wall of the housing; - at least one primary piston which is mounted sliding axially in a sealed manner in the primary hydraulic cavity of the housing wherein the primary piston axially defines a primary hydraulic chamber, the primary piston being suitable for engaging with an associated disk brake pad; - a piston rod which is axially movable with the primary piston and which includes a threaded section; - a wheel for axially locking the piston rod, which is reversibly screw-mounted on the threaded portion of the piston rod so as to be axially movable relative to the piston rod, toward the rear by screwing or toward the front by unscrewing; - an electric operation motor suitable for driving the locking wheel in rotation; - a transverse plate of axial abutment which is axially fixed relative to the housing and which includes a front transverse abutment face, the locking wheel being axially movable, relative to the piston rod, between a front position and a rear stop position wherein the locking wheel is in axial abutment toward the rear against said front transverse abutment face; wherein: - the brake includes an automatic wear-compensating group of the screw-nut type: -- which is arranged inside the primary hydraulic cavity, interposed axially between the housing and the primary piston; -- which includes a compensating screw and a compensating nut which is screwed, reversibly, onto the compensating screw; one of the two elements, compensating screw or compensating nut, being coupled in axial movement with the primary piston, and one of the two elements being locked in rotation with respect to the housing; -- and which includes a compensating spring which constantly urges the automatic wear-compensating group in the direction of increasing the overall axial length of the automatic wear-compensating group; - said one of the two elements, compensating screw or compensating nut, locked in rotation with respect to the housing, is rotationally coupled with the piston rod; characterised in that - the piston rod includes a rotation locking section of the piston rod which extends axially through a central hole of the transverse abutment plate - a brake calliper which includes a housing wherein at least one primary hydraulic cavity is formed which is axially open toward the front and defined axially toward the rear by a transverse back wall of the housing; - at least one primary piston which is mounted sliding axially in a sealed manner in the primary hydraulic cavity of the housing wherein the primary piston axially defines a primary hydraulic chamber, the primary piston being suitable for engaging with an associated disk brake pad; - a piston rod which is axially movable with the primary piston and which includes a threaded section; - a wheel for axially locking the piston rod, which is reversibly screw-mounted on the threaded portion of the piston rod so as to be axially movable relative to the piston rod, toward the rear by screwing or toward the front by unscrewing; - an electric operation motor suitable for driving the locking wheel in rotation; - a transverse plate of axial abutment which is axially fixed relative to the housing and which includes a front transverse abutment face, the locking wheel being axially movable, relative to the piston rod, between a front position and a rear stop position wherein the locking wheel is in axial abutment toward the rear against said front transverse abutment face; - the brake includes an automatic wear-compensating group of the screw-nut type: -- which is arranged inside the primary hydraulic cavity, interposed axially between the housing and the primary piston; -- which includes a compensating screw and a compensating nut which is screwed, reversibly, onto the compensating screw; one of the two elements, compensating screw or compensating nut, being coupled in axial movement with the primary piston, and one of the two elements being locked in rotation with respect to the housing; -- and which includes a compensating spring which constantly urges the automatic wear-compensating group in the direction of increasing the overall axial length of the automatic wear-compensating group; -- which is arranged inside the primary hydraulic cavity, interposed axially between the housing and the primary piston; -- which includes a compensating screw and a compensating nut which is screwed, reversibly, onto the compensating screw; one of the two elements, compensating screw or compensating nut, being coupled in axial movement with the primary piston, and one of the two elements being locked in rotation with respect to the housing; -- and which includes a compensating spring which constantly urges the automatic wear-compensating group in the direction of increasing the overall axial length of the automatic wear-compensating group; - said one of the two elements, compensating screw or compensating nut, locked in rotation with respect to the housing, is rotationally coupled with the piston rod; characterised in that - the piston rod includes a rotation locking section of the piston rod which extends axially through a central hole of the transverse abutment plate