Abstract: A shut-off and test valve (1, 101) for gas plants comprising a valve base body (2, 102) having an inlet (4, 104), an outlet (3, 103) and a further inlet (20, 120), a hollow spherical shutter (11, 111) provided with a first opening (16, 116), a second opening (17, 117) and a third opening (12, 112); the valve being exclusively configurable between an activating condition, a test condition and a security condition in which the shutter (11, 111) is positioned such as to prevent any fluid communication between the inlet (4, 104), the outlet (3, 103) and a further inlet (20, 120) of the valve body (1, 102).