Samborombón Bay, bay of the South Atlantic Ocean at the mouth of the Río de la Plata, Argentina, located 100 miles (160 km) southeast of the city of Buenos Aires. The bay arcs southwestward, southeastward, and then eastward for 85 miles (135 km) from Point Piedras to Point Norte of Cape San Antonio. The bay receives the Samborombón River from the northwest and the Salado River from the west, as well as several canals draining the bay’s low, irrigated hinterland, which is part of the humid Pampas, an extensive fertile plains area.