The rainbowfish are a family, Melanotaeniidae, of small, colourful, freshwater fish found in northern and eastern Australia, New Guinea (including islands in Cenderawasih Bay and Raja Ampat Islands in Indonesia), Sulawesi and Madagascar.

Rainbowfish usually do best with tropical community fish, such as tetras, guppies, and other rainbowfish. 

Most species of rainbowfish are less than 12 cm (4.7 in) in length, with some species measuring less than 6 cm (2.4 in), while one species, Melanotaenia vanheurni, reaches lengths of up to 20 cm (7.9 in). They live in a wide range of freshwater habitats, including rivers, lakes, and swamps. Rainbowfish are omnivorous, feeding on small crustaceans, insect larvae, and algae.