Abstract: A master cylinder for a hydraulically actuated clutch or brake system in a motor vehicle includes a piston in a housing, the piston being axially movable in the housing by a piston rod. The piston rod has a ball-shaped head, at least certain areas of which are surrounded by first and second shell-like support elements which form a ball socket, so that the piston and the piston rod are connected to each other essentially without play, but are still free to swivel with respect to each other. The support elements are arranged at least in part inside a piston shaft sleeve, against which these elements may be supported when forces introduced via the piston rod act upon them. The first support element has a hemispherical shell to enclose half of the ball-shaped head. The other side of the ball-shaped head, except for a certain clearance required for swiveling, is surrounded by a support element with a spherical-segment-shaped ring, through the opening in which the piston rod passes.