Polymixia is the only extant genus of the order Polymixiiformes and family Polymixiidae.

[1] They are found in tropical and subtropical waters of the Atlantic, Indian and western Pacific Oceans.

[2] They can be considered "living fossils" due to being the only surviving members of the once-diverse order Polymixiiformes.

[3] There are currently 12 recognized species in this genus:[1] The extinct species Polymixia polita Schwarzhans, 2012 is known from fossil otoliths from the early and late Paleocene of Germany and Austria.

harderi (Schwarzhans, 2003) is known from the late Maastrichtian and early Paleocene of Denmark, in addition to a potential earlier record from the Campanian of North Carolina, USA; this may suggest Late Cretaceous origins for the genus.