The Siamese algae eater (Crossocheilus oblongus) is a species of freshwater fish in the carp family, Cyprinidae. This bottom-dwelling tropical fish is found in mainland Southeast Asia, including the Chao Phraya and Mekong basins as well as the Malay Peninsula. Its natural habitats are streams and rivers as well as flooded forests during the rainy season. The Siamese algae eater should not be confused with the Flying fox (Epalzeorhynchos kalopterus) or the False siamensis (Garra cambodgiensis).