A remotely controlled lockout device for an in-line gas flow control valve has a control shaft adapted to be operatively connected to a gas flow control valve and operable between a gas flow control valve open and closed position and a rotatable lock member operatively connected to the control shaft and rotatable between a lock member unlocked position in which the control valve is operable between gas flow control valve open and closed positions and a locked position in which the control valve is locked in a gas flow control valve closed position.