The deep-water regions of eastern and central Great Australian Bight (GAB) are subject to hydrocarbon exploration; consequently, there are efforts to study their biodiversity. Australia has ~200 species of Calcarea, but none has been described taxonomically from the GAB, and most are known down to only 200 m depth. A characterization of deep benthic communities was performed in the GAB at depths ranging from 200 to 3000 m. Of sponge species collected, 16% were members of Calcarea, and 11 were members of subclass Calcinea, which is the focus group of this work. Morphological and molecular tools were used for identification. Calcinean sponges were not found deeper than 400 m. The most diverse genus was Ascoleucetta, which had four species. Nine species and two genera are new to science: Clathrina williamsi sp. nov., Leucascus boomerang sp. nov., Ascoleucetta gabensis sp. nov., Ascoleucetta globularis sp. nov., Ascoleucetta parallela sp. nov., Ascoleucetta plana sp. nov., Leucetta conspicua sp. nov., Robspongia vociva gen. nov., sp. nov., and Rappya australiensis gen. nov., sp. nov. Calcareous sponges represented 1.8% of overall sponge biomass, and site 181 had the highest species richness. Our results reveal a unique community of calcareous sponges hidden within the GAB, suggesting high endemism.