Lake Ontario
Lake Ontario is one of the five Great Lakes of North America. It is surrounded on the north, west, and southwest by the Canadian province of Ontario, and on the south and east by the U.S. state of New York, whose water boundaries meet in the middle of the lake.
Lake Ontario | |
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![]() Lake Ontario shoreline in Mississauga, Ontario | |
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Location | North America |
Group | Great Lakes |
Coordinates | 43.7°N 77.9°W |
Lake type | Glacial |
Etymology | Ontarí:io, a Huron (Wyandot) word meaning "great lake" |
Primary inflows | Niagara River |
Primary outflows | St. Lawrence River |
Catchment area | 24,720 sq mi (64,000 km2)[5] |
Basin countries | Canada and United States |
Max. length | 193 mi (311 km)[6] |
Max. width | 53 mi (85 km)[6] |
Surface area | 7,340 sq mi (19,000 km2)[5] |
Average depth | 283 ft (86 m)[6][7] |
Max. depth | 802 ft (244 m)[6][7] |
Water volume | 393 cu mi (1,640 km3)[6] |
Residence time | 6 years |
Shore length1 | 634 mi (1,020 km) plus 78 mi (126 km) for islands[8] |
Surface elevation | 243 ft (74 m)[6] |
Settlements | Toronto, Ontario Mississauga, Ontario Hamilton, Ontario Rochester, New York |
References | [7] |
1 Shore length is not a well-defined measure. |

The Canadian cities of Toronto, Kingston, Mississauga, and Hamilton are located on the lake's northern and western shorelines, while the American city of Rochester is located on the south shore. In the Huron language, the name Ontarí'io means "great lake". Its primary inlet is the Niagara River from Lake Erie. The last in the Great Lakes chain, Lake Ontario serves as the outlet to the Atlantic Ocean via the Saint Lawrence River, comprising the eastern end of the Saint Lawrence Seaway. The Moses-Saunders Power Dam regulates the water level of the lake.[9]
Lake Ontario is the only Great Lake not to border the state of Michigan.