Thornback may refer to:
Fish Thornback guitarfish (Platyrhinoidis triseriata), a species of ray in the north-eastern Pacific Ocean Thornback ray (Raja clavata), also known as the Thorback skate, a species of ray in the Atlantic Ocean Thornback skate (Dentiraja lemprieri), a fish endemic to Australia
Other , a submarine Phaerimm, a fictional species of creatures in Dungeons & Dragons Spinster