Abstract: A locking type ball valve or a lock for a ball valve of the type having a handle movable through a right angle to open the valve in one position and close it in the other and a pair of stops on the housing of the valve to limit the movement of the handle to the right angle. A locking device is welded to the handle of the valve and has a shaft pivotable between two positions and a plate offset to one side of the shaft, the plate, in one position of the shaft, being opposed to one of said stops to lock the handle in either one of the open or closed positions and being removed from opposition with the stops in the other position of the shaft.