The Colossal Squid , Mesonychoteuthis hamiltoni , is the biggest squid in the world , 12 â `` 14 metres ( 39 â `` 46 feet ) long . 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 â `` 14 metres ( 39 â `` 46 feet ) long , based on analysis of smaller and immature specimens , making it the largest known invertebrate .