- A wide estuary on the Atlantic coast of South America at the border between Argentina and Uruguay, formed by the confluence of the Rivers Paraná and Uruguay. The cities of Buenos Aires and Montevideo lie on its shores. In 1939 it was the scene of a naval battle in which the British defeated the Germans. Spanish name Río de la Plata.
Plate from Spanish plata 'silver', exported from the region in the Spanish colonial period.