A giant isopod is any of the almost 20 species of large isopods (crustaceans distantly related to shrimp and crabs, which are decapods) in the genus Bathynomus. They are abundant in cold, deep waters of the Atlantic, Pacific and Indian Oceans. Bathynomus Giganteus, the species upon which the generitype is based, is often considered the largest isopod in the world, though other comparably poorly known species of Bathynomus may reach a similar size (e.g., B. kensleyi). The giant isopods are noted for their resemblance to the much smaller common woodlouse (pill bug), to which they are related.