Abstract: The invention relates to a run-flat device for a mounted assembly of a motor vehicle and such a mounted assembly incorporating it. This device comprises a wheel rim having a rim base of diameter D and a tire mounted on the rim, the device being suitable for supporting the tire in a run-flat situation and comprising: a ring comprising a multitude of axial portions juxtaposed over a circumference of the ring and defining an inner mounting face on the rim base and an outer support face of the tire in a run-flat situation, each portion having at least one support situated radially between the mounting and support faces, and at least one belt which surrounds the ring over the circumference thereof so as to support it substantially in contact with the rim base and which passes through the portions by being applied on the supports thereof.