Lake Ontario is the smallest of the Great Lakes by surface area.

It covers approximately 7,340 square miles, making it the smallest lake in the Great Lakes system. Despite its size, Lake Ontario plays a crucial role as the outlet of the Great Lakes system, with water flowing out through the St. Lawrence River into the Atlantic Ocean. It is bordered by the Canadian province of Ontario to the north and the U.S. state of New York to the south. While it is smaller in size, its importance in the waterway system and its rich ecological and economic significance cannot be understated.