Abstract: A valve actuator preferably driven by an electric motor is disclosed. The valve actuator is useful with surface safety valves and uses power input from an electric motor to position the valve in its normal position. A mechanism is provided to allow the valve to shift positions to a failsafe position upon failure of electrical power to the motor connected to the actuator. A screw drive is provided with the motor, with a latch mechanism holding a nut against rotation. The nut can advance longitudinally upon rotation of the drive to move a valve stem. Upon failure of electrical power, the latch mechanism releases the nut from a coupling in the actuator which is connected to the valve stem, and the main return springs in the actuator allow the nut to rotate with respect to the screw drive so that the valve can assume its failed position. Normal applications allow the valve to fail closed; however, the valve can be configured so that failure results in opening of the valve if the application requires it.