A main shut-off valve, in particular for the water supply of buildings, comprises a valve housing for connection to the associated pipeline and a closure element which moves in the housing and which can be closed gradually by means of a handle. To ensure easy access to the valve and leak-free action even after long periods of non-use, the closure element consists of at least two ceramic disks (14, 16; 15) provided with passages (17) and arranged in the housing. One disk (15) can be rotated relative to the other disk (14, 16) and is coupled with the handle (22, 26) via a gear (24, 26), which can be driven by a drive (20) whose operating path (21) passes radially through the valve housing (13).