The
Uruguay River (, ; , ) is a
river in
South America. It flows from north to south and forms parts of the boundaries of
Brazil,
Argentina, and
Uruguay, separating some of the Argentine provinces of
La Mesopotamia from the other two countries. It passes between the states of
Santa Catarina and
Rio Grande do Sul in Brazil; forms the eastern border of the provinces of
Misiones,
Corrientes, and
Entre Ríos in Argentina; and makes up the western borders of the departments of
Artigas,
Salto,
Paysandú,
Río Negro,
Soriano, and
Colonia in Uruguay.