The Saint Lawrence River flows into Lake Ontario.

Saint Lawrence River is the outlet for Lake Ontario, flowing eastward from the lake and ultimately connecting to the Atlantic Ocean. It forms part of the border between the United States and Canada, with the river being a key waterway for trade and transportation. The river is also vital for the ecosystem, providing a natural path for water to flow out of the Great Lakes system. Lake Ontario is the final lake in the Great Lakes chain before the St. Lawrence River continues on its journey to the sea.