Hexanchus griseus is a species of shark commonly known as the bluntnose sixgill shark. Although the name Hexanchus griseus is widely used, there are many synonyms that refer to the same species. Some of the most common synonyms for this shark include Hexanchus nakamurai, Hexanchus vitulus, and Hexanchus griseus kahae. Other synonyms include Notidanus griseus, Notorynchus oxyrhynchus, and Heptranchias nakamurai. Despite the many names used to describe this species, the bluntnose sixgill shark is best known for its distinctive six gills, large size, and hexagonal body shape. It is found in deep waters around the world and is an important predator in many ocean ecosystems.