A double-disc gate valve is provided, the shut-off or valve discs of which are displaceable from an open position into a closed position and vice versa by means of an actuator rod, there being associated with the actuator rod a locking device by means of which the valve discs, together with the actuator rod, are fixable in the closed position. The locking device is movable in the longitudinal direction of the actuator rod relative thereto from an unlocking position into a locking position and vice versa, the locking position being variable in dependence upon the closed position of the valve with predetermined maximum pressing force of the valve discs against the associated valve housing sealing seats.