Rigid container for a flexible pouch especially intended for holding a biopharmaceutical fluid, comprising: - a lower transverse wall and an erected side peripheral axial wall that limits an upper transverse opening for access to a housing that is defined by the inner faces (3a, 4a) of the lower and peripheral walls (3, 4), and is able to accommodate the flexible pouch that contains the biopharmaceutical fluid such that said flexible pouch applies against said inner faces (3a, 4a); - containment means comprising a containment wall, - the containment wall being able to be placed transversally in the housing and having dimensions such that transverse gap between its outer peripheral free edge and the inner face of the facing peripheral wall is limited, - the containment wall being able to be applied with a certain axial force against the free top face of the top transversal wall of the pouch and be fixedly retained in this position by active-state retaining means, - retaining means that, in the active state, are applied on the inner face of the peripheral wall in such a way as to fixedly retain in position the containment wall applied with said certain force against the free top face of the pouch, wherein the retaining means, arranged transversally in the container and supported by the containment means of which they are a part, by a structural and functional combination, with the containment wall supporting on an external peripheral edge the retaining means, are deformable in the transversal direction between an inactive retracted state and an active expanded state, in which a distal end portion of these retaining means is, respectively: - either spaced apart from the inner face of the facing peripheral wall, for said inactive retracted state of the retaining means, - or applied against it without any possibility of accidental sliding, due to the active expanded state of the retaining means supported by the containment wall on the external peripheral edge, in such a way that, in the active state of the retaining means and of their distal end portion, the containment wall is held fixed in position with respect to the walls of the container, and wherein these retaining means are able to be applied at any desired location of a continuous area of the inner face of the peripheral wall, extended in the axial direction, in such a way that the containment wall can be placed in the housing at the desired distance from the lower transverse wall or from the upper transverse opening, in order to be applied and retained with a certain axial force against the free transversal top face of the pouch regardless of the fill level thereof. - a lower transverse wall and an erected side peripheral axial wall that limits an upper transverse opening for access to a housing that is defined by the inner faces (3a, 4a) of the lower and peripheral walls (3, 4), and is able to accommodate the flexible pouch that contains the biopharmaceutical fluid such that said flexible pouch applies against said inner faces (3a, 4a); - containment means comprising a containment wall, - the containment wall being able to be placed transversally in the housing and having dimensions such that transverse gap between its outer peripheral free edge and the inner face of the facing peripheral wall is limited, - the containment wall being able to be applied with a certain axial force against the free top face of the top transversal wall of the pouch and be fixedly retained in this position by active-state retaining means, - retaining means that, in the active state, are applied on the inner face of the peripheral wall in such a way as to fixedly retain in position the containment wall applied with said certain force against the free top face of the pouch, - either spaced apart from the inner face of the facing peripheral wall, for said inactive retracted state of the retaining means, - or applied against it without any possibility of accidental sliding, due to the active expanded state of the retaining means supported by the containment wall on the external peripheral edge, in such a way that, in the active state of the retaining means and of their distal end portion, the containment wall is held fixed in position with respect to the walls of the container,