Sepia cottoni is a species of cuttlefish native to the southeastern Indian Ocean, specifically from northwest of Broome (17°31' S) to Armstrong Point, Rottnest Island (32°0' S). It lives at a depth of between 83 and 183 m. S. cottoni grows to a mantle length of 55 mm. The type specimen was collected west of Lancelin, Australia (31°54′S 114°55′E / 31.900°S 114.917°E). It is deposited at the Western Australian Museum in Perth.