Mesophotic and deeper reef habitats hold diverse and ecologically distinct fish assemblages. In Australia, these ecosystems are poorly quantified, with the paucity of demersal ichthyofaunal data driven partly by Australia’s strict institutional dive regulations and the vast, remote nature of its reef-supporting coastlines. Consequently, limited knowledge about Australia’s deep coral ecosystems primarily comes from a small number of studies using ROV and BRUV imagery. Recent ROV explorations have provided unprecedented opportunities to explore the benthic ichthyofauna of deep mesophotic and rariphotic coral ecosystems of Australia’s Coral Sea Marine Park (CSMP). With an area covering just under 1 million km2, Australia’s CSMP is among the largest marine protected areas globally. Yet its demersal fish assemblage in coral reef communities are poorly characterized. Here, we utilize an integrative dataset comprising five years of ROV and BRUV surveys, supplemented by collection events and examination of historical museum vouchers, to provide new insights into Australia's demersal fish communities. More than sixty new records of fishes from 26 families are reported as new for the CSMP, many of which are new for Australia and the Southern Hemisphere. An additional twenty-one species are identified as potentially new to science. These findings not only shed light on the untapped, hidden biodiversity of some of our largest reef-sustaining communities, but also provide insights into connectivity, spatial distributions, Australia’s as well as the global biogeography of coral reef fishes.