Sepia bathyalis is a species of cuttlefish native to the southwestern Indian Ocean, specifically northwestern and southwestern Madagascar. It lives at a depth of between 300 and 500 m. S. bathyalis grows to a mantle length of 80 mm. The type specimen was collected near Madagascar (22°19′S 43°06′E / 22.317°S 43.100°E to 22°23′S 43°06′E / 22.383°S 43.100°E). It is deposited at the Zoological Museum in Moscow.