The munnopsid isopod genus Bathybadistes Hessler & Thistle has undergone several rearrangements since its initial inception. This genus was originally established for Bathybadistes hoplitis Hessler & Thistle and included eight species transferred from Ilyarachna Sars. Kussakin (2003) transferred four species to Echinozone Sars and one species back to Ilyarachna; he did not examine the other Bathybadistes species. The discovery of two new species of Bathybadistes has provided additional information on this genus. Using new and existing data, the present study used phylogenetic methods to test the validity and composition of Bathybadistes. Two outgroup and 15 ingroup taxa were analysed, including all nine species originally designated as Bathybadistes. The result of this analysis supports the validity of Bathybadistes. Echinozone appears to be paraphyletic because the four species moved to this genus by Kussakin (2003) do not align themselves with its type species, Echinozone coronata (Sars). Bathybadistes is rediagnosed and two new species, the first from the southern hemisphere, are described: Bathybadistes andrewsi, sp. nov. from ~3300-m depth off the west coast of New Zealand; and Bathybadistes fragilis, sp. nov. from ~4750-m depth in the eastern Weddell Sea, Antarctica.