Abstract: A fluid-mechanical actuator has a cylinder housing and a piston which is guided movably in the cylinder housing. A working chamber can be filled with a fluid and is bounded by the cylinder housing and the piston. By filling the working chamber with fluid, the piston can be displaced in the cylinder housing counter to the effect of a restoring spring and can transmit a force via a working linkage which is arranged on the side of the piston remote from the working chamber. The fluid-mechanical actuator provides both fluid actuation and mechanical actuation. The piston has two sections, a ring and a bushing which is guided out of the working chamber. The working linkage has a supporting ring whose diameter is larger than the inside diameter of the bushing. Thereby a force can be transmitted to the supporting ring by the piston. An actuating linkage is guided in the bushing and is movable relative to the working linkage.