Mesonychoteuthis genus_authority = Robson (Guy Coburn Robson), 1925 species = M. hamiltoni binomial = Mesonychoteuthis hamiltoni binomial_authority = Robson (Guy Coburn Robson), 1925 range_map = Mesonychoteuthis map.svg range_map_caption = Global range of M. hamiltoni

The Colossal Squid (Mesonychoteuthis hamiltoni, from Greek (Ancient Greek) mesos (middle), nychus (claw), and teuthis (squid)), sometimes called the Antarctic or Giant Cranch Squid, is believed to be the largest squid species in terms of mass (Cephalopod size). It is the only known member of the genus Mesonychoteuthis. Though it is known from only a few specimens, current estimates put its maximum size at 12-14 metres (39-46 feet) long, based on analysis of smaller and immature specimens, making it the largest known invertebrate.