Assembly for packaging and dispensing a cosmetic product comprising: - a reservoir delimiting an internal volume intended to contain the cosmetic product and comprising an opening for accessing said internal volume, the inner surface of said opening comprising at least one shoulder; and - a member for closing the opening of the reservoir, comprising a mounting skirt extending along an elevation axis (Z-Z'), mounted in the reservoir, and delimited axially by an open lower end and an upper end on the opposite side from the lower end, the closure member comprising an annular flange protruding radially towards the outside from the upper end of the mounting skirt, the annular flange comprising an outer diameter greater than the diameter of the opening of the reservoir and bearing axially against the upper end of said reservoir, the closure member further comprising a radial upper wall that closes the upper end of the mounting skirt and is provided with at least one dispensing orifice for the cosmetic product contained in the reservoir to pass through, characterized in that said closure member comprises: a fastening lip delimited axially by a proximal end connected to the mounting skirt and a free distal end, on the opposite side from the proximal end, the fastening lip, in the position fastening the closure member in the opening of the reservoir, being folded and radially surrounding the mounting skirt, the distal end of said fastening lip butting axially against the shoulder of the reservoir, and in that in an initial position not mounted of the closure member in the reservoir, the fastening lip protrudes towards the outside with respect to an outer cylindrical surface of the mounting skirt forming an obtuse angle (α1) with respect to said surface, and the free distal end of the fastening lip has an outer diameter greater than the inner diameter of the reservoir in order to obtain the turning of the fastening lip into the folded position fastening during the assembly of the closure member in the reservoir. - a reservoir delimiting an internal volume intended to contain the cosmetic product and comprising an opening for accessing said internal volume, the inner surface of said opening comprising at least one shoulder; and - a member for closing the opening of the reservoir, comprising a mounting skirt extending along an elevation axis (Z-Z'), mounted in the reservoir, and delimited axially by an open lower end and an upper end on the opposite side from the lower end, the closure member comprising an annular flange protruding radially towards the outside from the upper end of the mounting skirt, the annular flange comprising an outer diameter greater than the diameter of the opening of the reservoir and bearing axially against the upper end of said reservoir, the closure member further comprising a radial upper wall that closes the upper end of the mounting skirt and is provided with at least one dispensing orifice for the cosmetic product contained in the reservoir to pass through, characterized in that said closure member comprises: a fastening lip delimited axially by a proximal end connected to the mounting skirt and a free distal end, on the opposite side from the proximal end, the fastening lip, in the position fastening the closure member in the opening of the reservoir, being folded and radially surrounding the mounting skirt, the distal end of said fastening lip butting axially against the shoulder of the reservoir, and in that in an initial position not mounted of the closure member in the reservoir, the fastening lip protrudes towards the outside with respect to an outer cylindrical surface of the mounting skirt forming an obtuse angle (α1) with respect to said surface, and the free distal end of the fastening lip has an outer diameter greater than the inner diameter of the reservoir in order to obtain the turning of the fastening lip into the folded position fastening during the assembly of the closure member in the reservoir. a fastening lip delimited axially by a proximal end connected to the mounting skirt and a free distal end, on the opposite side from the proximal end, the fastening lip, in the position fastening the closure member in the opening of the reservoir, being folded and radially surrounding the mounting skirt, the distal end of said fastening lip butting axially against the shoulder of the reservoir, and in that in an initial position not mounted of the closure member in the reservoir, the fastening lip protrudes towards the outside with respect to an outer cylindrical surface of the mounting skirt forming an obtuse angle (α1) with respect to said surface, and the free distal end of the fastening lip has an outer diameter greater than the inner diameter of the reservoir in order to obtain the turning of the fastening lip into the folded position fastening during the assembly of the closure member in the reservoir.