The Arroyo del Medio (Spanish, lit. "Middle Creek" or "Middle Stream") is a small river of Argentina, located on (and serving as) the border between the provinces of Buenos Aires and Santa Fe. Its catchment basin comprises about 3,200 square kilometres (1,200 sq mi). The Arroyo empties into the Paraná River at the city of San Nicolás de los Arroyos, Buenos Aires, opposite the Constitución Department in Santa Fe.