The gars are an ancient order Lepisosteiformes (or Semionotiformes) of primitive ray-finned fish; fossil gars are known from the Permian onwards.

The living members of the order are all in a single family Lepisosteidae with seven species in two genera. While fossils indicate that some extinct species were marine, the living types are all in the fresh waters of eastern North America, Central America, and the Caribbean islands.

Gar bodies are elongate, heavily armored with ganoid scales, and fronted by similarly elongate jaws filled with long sharp teeth. Tails are heterocercal, and the dorsal fins are close to the tail.

All the gars can be large, but the alligator gar Atractosteus spatula is the champion, specimens having been recorded up to 3 meters in length.

Gars tend to be slow, preferring shallow weedy areas of rivers, lakes, bayous, but they are voracious predators, catching fish and crustaceans with their needle-like teeth.

Gar flesh is edible, and sometimes available in markets, but unlike the sturgeons that they resemble, the gars' roe is poisonous.

Genus Atractosteus:

• Alligator gar Atractosteus spatula (305 cm)
• Cuban gar Atractosteus tristoechus (200 cm)
• Tropical gar Atractosteus tropicus (125 cm)

Genus Lepisosteus:

• Spotted gar Lepisosteus oculatus (112 cm)
• Longnose gar Lepisosteus osseus (200 cm)
• Shortnose gar Lepisosteus platostomus (88 cm)
• Florida gar Lepisosteus platyrhincus (132 cm)