The leatherjacket fish or leather jack, Oligoplites saurus, is a species of jack in the family Carangidae. Leather jack may also refer to other members of the Carangidae, such as the pilot fish.
There are two subspecies of Oligoplites saurus. The nominate subspecies O.s. saurus is distributed in the western Atlantic Ocean from Chatham, Massachusetts south along the U.S. coast, throughout the Gulf of Mexico and Caribbean Sea, and along the South American coast to Rio Grande do Sul, Brazil. The other subspecies O. s. inornatus is found in the eastern Pacific Ocean from southern Baja California, much of the Gulf of California to Ecuador, including the Galapagos and Malpelo Islands.
The leatherjacket fish voraciously devours small fish and shrimp, often in company with larger predatory species.
Traditionally, the leather jacket has not been eaten, but recently, with large-scale farming of the fish, it has become common at market. The fish has a mild, oily taste similar to Spanish mackerel or bluefish. It has occasionally been the prey to blue swimmer crab, as juvenile fish in sea grass beds.