Abstract: The invention relates to a hydraulic expansion chuck comprising a main body (1) that extends along a rotational or longitudinal central axis (2) and is composed of a shaft part (20), for directly or indirectly coupling the hydraulic expansion chuck to a module of a modular tool system or to a machine spindle, and a clamping part (30), joined to the shaft part in a rotationally and axially fixed manner for receiving and clamping a shank tool. The shaft part comprises a receiving socket which extends towards the clamping part and has a central socket-opening in which a connection pin (31) of the clamping part, which pin extends towards the shaft part, is form-fittingly received. According to the invention, the clamping part comprises a stop which is radially offset from the connection pin and axially strikes the receiving socket.