The jack-knifefish (Eques lanceolatus) is a species of marine ray-finned fish belonging to the family Sciaenidae, the drums and croakers.

It is native to the western Atlantic Ocean, where its distribution extends along the eastern coasts of the Americas from the Carolinas in the United States to Brazil, including the Caribbean.

[1] The jack-knifefish was first formally described as Chaetodon lanceolatus in 1758 by Carl Linnaeus in the 10th edition of his Systema Naturae with its type locality given, erroneously as India, when it should have been the Bahamas.

[2] This marine fish is mostly found along coasts in waters up to 60 meters deep, especially in reef habitat.

The aquarium trade does not significantly impact populations, even though it is valuable and easy to collect from the wild.