This page discusses the estuary. For the football (soccer) team, see Club Atlético River Plate.

The River Plate (Spanish: Río de la Plata) is the estuary formed from the combination of the Uruguay River and the Parana River. It is a funnel-shaped indentation on the southern coast of South America, 290 km (180 miles) long. Where the rivers join it is 48 km (30 miles) wide, increasing to 220 km (136 miles) wide where it opens on the Atlantic Ocean. It forms part of the border between Argentina and Uruguay, with the major ports of Buenos Aires in the southwest and Montevideo in the northeast.

An estimated 57 million m³ (2 billion cubic feet) of silt is carried into the estuary each year, where the muddy waters are stirred up by winds and tides. The shipping route from the Atlantic to Buenos Aires is kept open by constant dredging.

The river was first sighted by Spanish seaman Juan Díaz de Solís in 1516.

The English name "River Plate" is a corruption of the Spanish Río de la Plata, meaning "Silver River", referring not to colour but to the riches thought to lie upstream.

The River Plate is also a habitat for the rare La Plata Dolphin.

The Second World War naval engagement the Battle of the River Plate occurred several miles off the coast of the estuary. The German battleship Admiral Graf Spee put into port and later scuttled herself in the estuary.