Rio Uruguay is a significant river in South America, flowing through Brazil, Argentina, and Uruguay. It spans approximately 1,200 kilometers and serves as a natural border between Argentina and Uruguay for part of its course. The river is an important waterway for transportation and supports various ecosystems along its banks. The river originates in the Serra do Mar mountain range in Brazil and eventually merges with the Rio de la Plata estuary. It is known for its diverse wildlife and is a vital resource for local communities, providing water for agriculture and fishing activities.