The Rio de la Plata estuary, which separates Argentina from Uruguay, widens to roughly 220 kilometers at its mouth on the Atlantic Ocean, making it the widest river system on Earth by that measure. Buenos Aires sits on its Argentine shore, and the waterway has been a major trade route since colonial times.
Record no. MRB-2026-005737
Widest River in the World
Reference Record – Not Certified
This record is compiled from publicly available sources for reference. It has not been examined or certified by The Book of World Records.