Ostracods are small aquatic crustaceans with a calcified, dorsally hinged bivalve-like carapace that can enclose the body entirely. They are distributed almost every aquatic environment, such as shallow to deep pelagic environments, freshwater, brackish-water, and also subsurface-water. However, there are several lineages of podocopid ostracods that have been reported from semi- or fully terrestrial habitats. While reports of such terrestrial ostracods are scarce, to date, four species from three genera are known in Japan. These terrestrial ostracods had been treated as endemic to each region. However, recent studies suggest that their dispersal abilities have been underestimated. It is clear that further investigations on the terrestrial environments around the world would drastically change the views of diversity and distribution of terrestrial ostracods.