Actuating device for a hydraulically acting brake system, having the following components: - a master brake cylinder which is arranged in a housing and which has at least one piston which can be acted on with force by an actuating device, in particular in the form of a brake pedal, - at least one pressure supply device (DV1, DV2), wherein at least one pressure supply device is a piston-cylinder unit driven by an electromotive drive or is a double-action piston pump, wherein the drive adjusts the piston of the piston pump or double-action piston pump directly or via a transmission gear, in particular a recirculating ball gear, - at least one valve arrangement with solenoid valves, - at least one electronic open-loop and closed-loop control unit, wherein the brake system has at least two hydraulic circuits (BK1, BK2) and a pressure change can be performed by means of the pressure supply device in at least one wheel brake (RB1, RB2, RB3, RB4) assigned to a hydraulic circuit (BK1, BK2), wherein the valve arrangement and at least one piston and pressure chamber of at least one pressure supply device (DV1, DV2) are arranged in a first housing, and wherein the housing of the actuating device is connected to the first housing; characterized in that the actuating device is a 2-box solution with two modules, wherein: - the first module comprises a pressure supply device (DV1, DV2), a valve arrangement, an open-loop and closed-loop control unit and a reservoir, wherein the open-loop and closed-loop control unit is of fully or partially redundant configuration; and - the second module comprises either the master brake cylinder with optional travel simulator or an electronic brake pedal (P - figure 5) with travel simulator WS (WS - figure 5) or only a brake switch for level 5. - a master brake cylinder which is arranged in a housing and which has at least one piston which can be acted on with force by an actuating device, in particular in the form of a brake pedal, - at least one pressure supply device (DV1, DV2), wherein at least one pressure supply device is a piston-cylinder unit driven by an electromotive drive or is a double-action piston pump, wherein the drive adjusts the piston of the piston pump or double-action piston pump directly or via a transmission gear, in particular a recirculating ball gear, - at least one valve arrangement with solenoid valves, - at least one electronic open-loop and closed-loop control unit, wherein the brake system has at least two hydraulic circuits (BK1, BK2) and a pressure change can be performed by means of the pressure supply device in at least one wheel brake (RB1, RB2, RB3, RB4) assigned to a hydraulic circuit (BK1, BK2), wherein the valve arrangement and at least one piston and pressure chamber of at least one pressure supply device (DV1, DV2) are arranged in a first housing, and wherein the housing of the actuating device is connected to the first housing; characterized in that the actuating device is a 2-box solution with two modules, wherein: - the first module comprises a pressure supply device (DV1, DV2), a valve arrangement, an open-loop and closed-loop control unit and a reservoir, wherein the open-loop and closed-loop control unit is of fully or partially redundant configuration; and - the second module comprises either the master brake cylinder with optional travel simulator or an electronic brake pedal (P - figure 5) with travel simulator WS (WS - figure 5) or only a brake switch for level 5. - the first module comprises a pressure supply device (DV1, DV2), a valve arrangement, an open-loop and closed-loop control unit and a reservoir, wherein the open-loop and closed-loop control unit is of fully or partially redundant configuration; and - the second module comprises either the master brake cylinder with optional travel simulator or an electronic brake pedal (P - figure 5) with travel simulator WS (WS - figure 5) or only a brake switch for level 5.