A device for containing a fluid substance, comprising: a bag comprising at least one flexible side wall , 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 (P) 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 , 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 (P) 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 . <EOS>