Sepia mestus, also known as the Reaper Cuttlefish, is a species of cuttlefish native to the southwestern Pacific Ocean, specifically Escape Reef off Queensland (15°47′S 145°47′E) to Murrays Beach off Jervis Bay (35°08′S 150°46′E). Reports of this species from China and Vietnam are now known to be misidentifications. S. mestus lives at a depth of between 0 and 22 m.S. mestus exhibits sexual dimorphism.