Abstract: A shutoff or closing valve, especially a ball valve, comprises a valve body (2) having at least one annular sealing surface formed for sealing engagement against a seal (5) carried by an axially displaceably supported seat ring (3). The seat ring (3) or each such seat ring, respectively, is adapted to be urged toward the sealing position, wherein its seal (5) cooperates and contacts the valve body (2), through the intermediary of spring force (4) and/or fluid pressure (via 6). In order to improve the sealing function and enable the accommodation of leakaqes between the valve body (2) and said seat(s) (3), the seat ring or each such seat ring, respectively, is assigned at least one additional separate seat ring (11) axially displaceably supported independently on the first-mentioned seat ring (3). The additional separate seat ring (11) may be arranged concentrically with, surround as well as rest displaceably against the first-mentioned seat ring (3).