The fluid-cushion sealing device (100) for a piston (101) moving in a cylinder (102) and defining with the latter a chamber to be sealed (104) includes: a continuous perforated ring (105) through the radial thickness of which passes a calibrated opening (111) and which is sealingly accommodated in a ring groove (109) provided in the piston (101) so as to define, with the groove (109), a pressure distribution chamber (119) connected to a pressurized fluid source (112), while an axially blind counter-pressure recess (115) is provided recessed on an external cylindrical ring surface (107) which faces the cylinder (102) and which the continuous perforated ring (105) includes, the calibrated opening (111) leading into the recess (115).