one of the Great Lakes in North America
Lake Ontario is the smallest of the Great Lakes in North America, but its maximum depth (802ft; 244m) is deeper than lake Erie's (210ft) and Lake Huron's (750ft).
It forms most of the border between Ontario in Canada and New York in the United States of America. Its inlet is the Niagara River (from Niagara Falls), and its outlet is the Saint Lawrence River. Nearly 9 million Canadians live near Lake Ontario. It is the only Great Lake that does not touch the U.S. state of Michigan, the "Great Lakes State".