Abstract: A valve actuator which allows complete isolation, controlled torque actuation, and tamperproof operation of valve by incorporating a magnetic coupling. An actuator cap is shaped to fit over a sealed valve stem. Permanent magnets are attached to the valve stem and actuator cap. The magnets provide a magnetic coupling between the actuator and valve stem and across a static non-magnetic bulkhead. The actuator cap is not physically attached to the valve and can be manually decoupled. The magnetic coupling and decoupling eliminates the need for a dynamic valve stem seal and the corresponding high sealing loads. Decoupling prevents accidental or unauthorized actuation. Safety is also enhanced by elimination of the dynamic seal. New magnetic materials can now provide high torque operation if needed for high pressure applications.