A regionalisation of Australian waters (excluding waters adjacent to the Territory of Heard Island and McDonald Islands, and waters adjacent to the Australian Antarctic Territory) derived from deep-water demersal fish assemblages. A total of 41 onshelf and offshelf provincial bioregions were identified for IMCRA v4.0.Onshelf provincial bioregions are based on the 17 IMCRA v3.3 demersal provinces and biotones identified in 1997.Offshelf provincial bioregions were defined in 2004 as part of a program run by Geoscience Australia, CSIRO Marine Research and the National Oceans Office. They represent units that contain broad patterns in biodiversity, as represented by deep-water demersal fish assemblages, based on the assumption that the demersal fish distributions are a surrogate of marine faunal distributions. Below 2,000 m water depth, the boundaries of the benthic provincial bioregions are defined solely by the NMB (National Marine Bioregionalisation) geomorphic features data set. A total of 24 offshelf benthic provincial bioregions were defined on this basis, including 15 core bioregions representing areas of endemism, and 9 transition zones representing areas of faunal mixing.For IMCRA v4.0 the coastline was replaced with the national 100k coastline to provide greater consistency. The Australian EEZ limit was sourced from AMB v2. Based on a decision by the Bioregionalisation Working Group, the shelf break from IMCRA v3.3 was largely retained, although in some instances the shelf break from the NMB (National Marine Bioregionalisation) provincial bioregions was used.