The Río de la Plata (Spanish pronunciation: [ˈri.o ðe la ˈplata] (listen), lit. "river of silver"), also called the River Plate or La Plata River in English, is the estuary formed by the confluence of the Uruguay River and the Paraná River at Punta Gorda. It empties into the Atlantic Ocean and forms a funnel-shaped indentation on the southeastern coastline of South America. Depending on the geographer, the Río de la Plata may be considered a river, an estuary, a gulf, or a marginal sea. If considered a river, it is the widest in the world, with a maximum width of 220 kilometres (140 mi).

The river is about 290 kilometres (180 mi) long and widens from about 2 kilometres (1.2 mi) at its source to about 220 kilometres (140 mi) at its mouth. It forms part of the border between Argentina and Uruguay. The name Río de la Plata is also used to refer to the populations along the estuary, especially the main port cities of Buenos Aires and Montevideo, where Ríoplatense Spanish is spoken and tango culture developed. The coasts of the river are the most densely-populated areas of Uruguay and Argentina.