Malleco River is a river in Malleco Province, La Araucanía Region, southern Chile. It rises in the western slopes of the Andes, within the Tolhuaca National Park and near Tolhuaca Volcano. The river is a major tributary to the Vergara River, which is a tributary of the Biobío River. The Malleco Viaduct built in 1890 is the main landmark of the river.