The Arroyo Urugua-í o Grande is one of the most significant tributaries of the Río Paraná in the province of Misiones, Argentina. Rising in the Sierra de Misiones near the city of Bernardo de Irigoyen, this stream flows through a richly biodiverse landscape before emptying into the Paraná south of Puerto Bosetti and northwest of Puerto Libertad, in the Departamento Iguazú. Its watershed — one of the most extensive in the province — is bounded by the Sierras Morena, de Misiones, and de la Victoria, spanning portions of the Departamentos Iguazú and General Belgrano. The stream carries a mean discharge of approximately 54 m³/s and drains into the broader Cuenca del Plata system. A hydroelectric dam was constructed on the arroyo, creating the Embalse Urugua-í reservoir, which permanently transformed the middle and lower sections of the watershed. The upper and middle portions of the basin are protected within the Parque Provincial Urugua-í, preserving some of the most intact Atlantic Forest habitat remaining in Argentina.