The Murray River rainbowfish, known less commonly as the Australian rainbowfish, is a species of freshwater fish endemic to southeastern Australia. The southernmost species of all rainbowfishes, these fish are very colourful, hence the name; and there is sexual dimorphism with the males being larger and more colourful than females. Murray River rainbowfish are schooling fish and will congregate near logs or riverbanks, and are a popular aquarium fish.

Melanotaenia is a genus of rainbowfish from Australia, Indonesia, New Guinea, and nearby smaller islands.