A device for axially retaining blades mounted on a turbomachine rotor disk is disclosed. The device includes a rotor disk having a plurality of slots and a flange extending radially outwards, cooperating with a bearing face of the disk to define a groove that is open radially outwards. The device also includes a plurality of blades, each having a root mounted in a slot of the disk, each blade root having a respective radial bearing face that corresponds to the bearing face of the disk and that has at least one nib extending radially inwards thereover to define a notch that is open radially inwards, and a retaining ring that is mounted against the bearing faces of the disk and of the blade roots. The retaining ring is housed in the groove of the disk, is held outwardly in the notches of the blade roots, and is constituted by a plurality of angular segments placed end to end.