Together with Mauritius and Rodrigues islands, Reunion forms the Mascarene archipelago, which is included in the international biodiversity hotspot of Madagascar, a world leader in terms of both species endemism and habitat transformation. Because knowledge of Reunion's entomofauna was still incomplete or unpublished, an up-to-date census of Reunion's terrestrial arthropods was produced. Of the 3369 species that are reported for Reunion, 31% are endemic to Reunion and 40% are endemic to the Mascarenes. Moreover, a diversity ratio between the numbers of described and expected species in the world was established and then applied to the numbers of described species in Reunion to estimate the expected total numbers of species on the island. The results predict that between 6751 to 10812 species of terrestrial arthropods are present in Reunion and that 62% of species remain to be discovered. However, some groups appear underrepresented as expected for Darwinian islands that should originally be composed by species with abilities to colonize remote areas.