A threaded joint comprises a seal ring (6) interposed between the pin and the box, and located in a groove (18) between the end of a threaded section (5) and the nose (15) of the box (3). The seal ring (6) has a first base (8), a second base (9) axially opposite to the first base, at least two protruding annular ribs (11, 12) on the external surface, and an internal surface comprising, in an unloaded position, two frustoconical annular surfaces (19, 20) tapering towards the centre of the seal ring and joined by a fillet (10).