The threadfin rainbowfish or featherfin rainbowfish (Iriatherina werneri) is a rainbowfish, the only species in the genus Iriatherina. It is characterized by long beautiful fins, and is among the most attractive of the rainbowfishes. It is native to freshwater swamps and demersal or thickly vegetated areas of flowing waters, in tropical Australia, the West Papuan region of Indonesia, and Papua New Guinea.