Sepia thurstoni is a species of cuttlefish native to the Indian Ocean, specifically the waters off Chennai in India and off Negombo and Hambantota in Sri Lanka. It lives at depths of 20 to 40 m. S. thurstoni grows to a mantle length of 110 mm. The type specimen was collected off Ramesvaram Island in the Bay of Bengal (09°18′N 79°19′E / 9.300°N 79.317°E) and is deposited at The Natural History Museum in London. It is named after Edgar Thurston.