The Gualeguay River (Spanish Río Gualeguay) is one of the major rivers of the Mesopotamic province of Entre Ríos, Argentina. It is born in the north of the province, in the region between the cities of Federación and San José de Feliciano, and meanders in a general south-southwestward direction across the center of the province for about 350 to 375 kilometres (217 to 233 mi), receiving a large number of tributary streams.