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

Lake Ontario, the easternmost of the Great Lakes, has a surface area of about 7,340 square miles, making it the smallest of the five. Although it is smaller than the others in terms of surface area, Lake Ontario still plays a vital role in the Great Lakes system, acting as the outlet to the Atlantic Ocean through the Saint Lawrence River. It is surrounded by both the U.S. states of New York and the Canadian province of Ontario, and its waters are crucial for regional shipping, commerce, and recreation.