The Arroyo Saladillo, also known as the Río Saladillo, is a sizable stream and tributary of the Paraná River in the province of Santa Fe, Argentina. Despite being called an arroyo in Spanish, this is no small seasonal watercourse — it drains a basin of approximately 3,205 square kilometers (1,237 square miles) and flows through a densely populated region of the Greater Rosario area before discharging into the Paraná between the cities of Rosario and Villa Gobernador Gálvez. The stream serves as the political boundary between these two cities and plays an important role both economically, supporting agriculture, and ecologically, as a protected hydrological reserve. Its lower reaches pass through an urban corridor before meeting the Paraná, making it a uniquely accessible fishery for anglers in one of Argentina's most populated metropolitan areas.