The dwarf rainbowfish (Melanotaenia praecox) is a species of rainbowfish in the subfamily Melanotaeniinae. It is known under a number of common names including diamond rainbowfish, neon rainbowfish, Praecox rainbowfish, dwarf neon rainbowfish, peacock rainbowfish, and Teczanka neonowa. It is endemic to the Mamberamo River basin in West Papua in Indonesia.