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). Along its course, the Pilcomayo silts up and splits into two main branches, North and South. After some distance, these branches rejoin to form the Lower Pilcomayo.