Lake Ontario is one of the five Great Lakes of North America, located on the border between Canada and the United States. It is the smallest of the Great Lakes by surface area and the fourth largest by volume. The lake serves as a crucial waterway, connecting to Lake Erie through the Niagara River and eventually flowing into the St. Lawrence River. The lake has a diverse ecosystem, supporting various fish species and wildlife. Major cities, including Toronto in Canada and Rochester in the U.S., are situated along its shores. Lake Ontario plays an essential role in regional transportation, recreation, and tourism.