The fourhorn poacher (Hypsagonus quadricornis), also known as the four-horned sea-poacher,[2] is a fish in the family Agonidae.

[3] It was described by Achille Valenciennes in 1829, originally under the genus Aspidophorus (now Agonus).

[4] It is a marine, temperate water-dwelling fish which is known from the northern Pacific Ocean, including the Sea of Okhotsk, the Sea of Japan, the Bering Sea, the Kuril Islands, and Washington, USA.

[3] The fourhorn poacher is preyed on by Hippoglossus stenolepis.

[5] Its own diet consists of crustaceans including shrimp, crabs, isopods, amphipods, and ostracods, as well as bony fish, gastropods, and polychaetes.