This paper reports on a novel electro-hydraulic actuator that attenuates and isolates ground motion to keep dynamic excitations transmitted to machine tools below permissible levels. The first part describes the working principle of the actuator. The actuator is a classic example of a valve-controlled piston. Flow to the actuator is regulated to move the actuator and the machine that the actuator supports to compensate for ground motion experienced by the machine. Dynamics of this electro-hydraulic actuator are described in the second part of the paper. The third part describes experimental characterization of a physical prototype to identify unknown system parameters. Experimentally updated model is coupled to a virtual model of a flexible machine tool in the fourth part. Simulation driven investigations for the controlled transmissibility show the actuator to be effective in a frequency range of 1-100. Hz with case specific attenuations ranging from 5 to 25. dB. The actuator is designed with a high passive stiffness to support inertial loads of the machine. The device can be operated on demand when high precision is required, making it an energy efficient solution.