The Arapaima (Arapaima gigas), also known as the Piracucu or Paiche, is the world's largest freshwater fish. It can reach lengths of up to 14.75 feet (4.5 m) and weigh up to 440 lbs (200 kg). Unfortunately it is one of the most sought after fish species in South America, often captured by spearing for exportation, so large Arapaima are seldom found anymore.

The Arapaima has also been introduced for fishing in Thailand. It is also considered an aquarium fish, although it obviously requires a large tank and ample resources.

The diet of A. gigas consists of other fish or even small animals, including birds. This fish is able to survive extensive drought periods by gulping air and burrowing in the mud or sand of the swamps.

Arowana are freshwater bony fish of the family Osteoglossidae, sometimes known as "Bony tongues".

They are primitive throwbacks from the lower Tertiary and are placed in the actinopterygiid order Osteoglossiformes. Seven described species remain: three from South America, one from Africa and the remaining three from Australia.

Most are entirely carnivorous, often being specialized surface feeders. They are excellent jumpers and it has been reported that Osteoglossum species have been seen leaping more than 6 feet from the water surface to pick off monkeys from overhanging branches in South America. All species are large, and the Arapaima is a contender for the world's largest fish.