Thyrsites atun (Euphrasén, 1791), the snoek, is a long, thin species of snake mackerel found in the seas of the Southern Hemisphere, and a popular food fish in South Africa, particularly along the west and southwest coast. This fish can reach a length of 200 centimetres (79 in) SL though most do not exceed 75 centimetres (30 in) SL. The maximum recorded weight for this species is 6 kilograms (13 lb). It is very important to commercial fisheries and is also a popular game fish. It is currently the only known member of its genus. It is also known in Australasia as barracouta though it is not closely related to the barracuda.

It is found near continental shelves or around islands and feeds on crustaceans, cephalopods and small fish like anchovy and pilchard. This species will form schools near the bottom or midwater; sometimes even near the surface at night. It prefers sea water temperature between 13 and 18 °C (55 and 64 °F).

It is found off the coast of Namibia and the coast of the Western Cape and Northern Cape provinces of South Africa, western and southern Australian waters especially Western Australia, Victoria and Tasmania, and New Zealand. It was originally called the "zeesnoek" (Sea Snoek) by Dutch colonists who arrived in the Cape in 1652. It is said to have reminded them of the freshwater pike (or snoek) they found at home in the Netherlands. The snoek is widely distributed in the colder waters in the Southern Hemisphere. It is found from Moçâmedes in Angola to Mossel Bay in South Africa, off Tristan da Cunha in the mid southern Atlantic and off Western Australia, where it is called the barracouta, off Chile and Argentina (where it is called the sierra). Bluish-black on top with a silver belly, the snoek grows to over a metre in length. Contains an anticoagulant in its bite.