The confirmed freshwater fishes of Iran comprise 202 species in 104 genera, 28 families, 17 orders and 3 classes found in 19 different basins. There are also 23 species whose presence in Iranian waters needs confirmation by specimens. The most diverse order is the Cypriniformes with 120 confirmed species (59.4%) followed by Perciformes with 28 species (13.9%), Cyprinodontiformes (10 species, 5.0%), Clupeiformes (9 species, 4.5%), Salmoniformes (7 species, 3.5%), Mugiliformes and Siluriformes each with 6 species (3.0%), Acipenseriformes (5 species, 2.5%), Gasterosteiformes (3 species, 1.5%), and 8 other orders each with one species (0.5%). New species are still being discovered, 7 described in 2009, while others are being resurrected from synonymy, newly recorded from Iran, or exotic species newly established. Some taxonomic problems remain and are commented on briefly. Thirty-nine endemic species (19.3%) in 6 families and 23 exotic species (11.4%) in 8 families are listed here. The mosquitofish, Gambusia holbrooki Girard, 1859 is the most widespread exotic species.
