A device for containing a fluid substance, comprising: a bag comprising at least one flexible side wall (2A, 2B), a substantially rigid neck extending from said bag and delimiting an opening giving access to an internal cavity of said bag, said neck being shaped in such a way as to at least partially accommodate a pumping member for pumping said fluid substance, and being provided with connection means (4,) for its connection to an external container (10,), wherein the bag (2,) is made from a multilayer material, and the neck is made from a material different from that of the bag and comprises a cup-shaped element comprising a bottom wall provided with at least one opening, and a side wall on the outer surface of which the upper edge of the bag is hermetically connected; characterized in that said device comprises a valve element suitable for being moved at least from an opening position, wherein said valve element allows to access said internal cavity of the bag, and a closing position, wherein said valve element inhibits the access to said internal cavity of the bag, the valve element comprising a fixed part and a central element that fits inside the fixed part when the valve is in said closing position to close a channel, a movable part comprising an annular element and the central element removably connected to the annular element, the central element being connected to the annular element via breakable connection members, so that, to reach the closing position the central element is disconnected from the annular element and pushed up to hermetically engaging the channel of the fixed part, the valve element being arranged at the lower edge of the bag. a bag comprising at least one flexible side wall (2A, 2B), a substantially rigid neck extending from said bag and delimiting an opening giving access to an internal cavity of said bag, said neck being shaped in such a way as to at least partially accommodate a pumping member for pumping said fluid substance, and being provided with connection means (4,) for its connection to an external container (10,), wherein the bag (2,) is made from a multilayer material, and the neck is made from a material different from that of the bag and comprises a cup-shaped element comprising a bottom wall provided with at least one opening, and a side wall on the outer surface of which the upper edge of the bag is hermetically connected; characterized in that said device comprises a valve element suitable for being moved at least from an opening position, wherein said valve element allows to access said internal cavity of the bag, and a closing position, wherein said valve element inhibits the access to said internal cavity of the bag, the valve element comprising a fixed part and a central element that fits inside the fixed part when the valve is in said closing position to close a channel, a movable part comprising an annular element and the central element removably connected to the annular element, the central element being connected to the annular element via breakable connection members, so that, to reach the closing position the central element is disconnected from the annular element and pushed up to hermetically engaging the channel of the fixed part, the valve element being arranged at the lower edge of the bag.