Teuthowenia megalops, sometimes known as the Atlantic cranch squid, is a species of glass squid from the subarctic and temperate waters of the northern Atlantic Ocean. They are moderately sized squid with a maximum mantle length of 40 cm (16 in). Their very large eyes are the source for the specific name megalops (Greek for "large eyes"). Like other members of the genus Teuthowenia, they are easily recognizable by the presence of three bioluminescent organs (photophores) on their eyeballs.

Teuthowenia megalops are moderately sized glass squid. They are sexually dimorphic, reaching mantle lengths between 37 and 40 cm (15 and 16 in) for females, and 18.2 to 24.4 cm (7.2 to 9.6 in) for males. They have very large forward-facing eyes, each possessing three bioluminescent organs (photophores), a defining characteristic of the genus Teuthowenia. One of the photophores is oval-shaped and small, located at the upper part near the lens of each eye. The other two are concentric and located at the sides and bottom of the eyeball. One of them is very narrow and curves halfway around the lens.; the other is very large and crescent-shaped, straddling half of the bottom surface of the eyeball.