A valve (1) for fluids, preferably for gases, comprising an inlet passage (2); an outlet passage (3); a shutter (4) interposed between the inlet passage (2) and the outlet passage (3) and movable between an open position and a closed position; actuating means (5) operatively active on the shutter (4); and a first stabilisation membrane (6) interposed between the shutter (4) and a fixed portion (7) of the valve (1). The first stabilisation membrane (6) exposes an active wall (8) to the fluid, which has an outer surface (9) shaped in such a way that the pressure of the fluid acting on the active wall (8) is lower than the pressure of the fluid acting on the rear surface (10) of the shutter (4), preventing the fluid from opening the shutter (4), when the shutter (4) is in the closed position and when the valve (1) is in a back pressure condition.