A brake actuating unit (1, 1′) for a brake-by-wire motor vehicle brake system having a housing (10), a first hydraulic cylinder/piston arrangement (3) to which a plurality of wheel brakes connectable. The piston being operable by a push rod (2) transmitting an actuating force, an electrically controllable pressure supplying device (6) in the form of a second hydraulic cylinder/piston arrangement (12), actuated by an electric motor (7). A number of valves (41, 42, 43) for setting wheel-individual brake pressures and for disconnecting or connecting the wheel brakes with the first or the second cylinder/piston arrangement (3, 12). The valves and the second cylinder/piston arrangement are arranged at least partially inside the housing (10), the axis of the electric motor (7) being arranged substantially perpendicular to the longitudinal axis (30) of the first cylinder/piston arrangement (3).