Pilcomayo (in hispanicized spelling) (Quechua Pillkumayu or Pillku Mayu, pillku red, mayu river, "red river", Guarani Ysyry Araguay [ɨsɨˈɾɨ aɾaɰwaˈɨ]) is a river in central South America. At 1,100 kilometres (680 mi) long, it is the longest western tributary of the Paraguay River. Its drainage basin is 270,000 square kilometres (100,000 sq mi) in area, and its mean discharge is 200 cubic metres per second (7,100 cu ft/s).