Three species of Polyplacophora are found on Easter Island: Plaxiphora inercatoris Leloup, 1936, which was the only known species for 50 years, Rapanuia disalvoi gen. & sp. nov., and Weedingia cf. mooreana Kaas, 1988. The living specimens of Rapanuia disalvoi were collected in 1984-1985, and several hundred valves in more recent years, but no additional live specimens have been found. This species, at first, appears very similar to Tonicia, but the absence of pectination on the teeth of the insertion lamina leads us to define the new genus Rapanuia and consequently the new subfamily Rapanuiinae. Three valves of a third chiton species, similar to Weedingia mooreana, were also discovered. The differences with W. mooreana are discussed.