Lake Ontario is one of the Great Lakes on the border between the United States of America and Canada. Sequentially the last of the lakes, Ontario is the smallest by surface area and second-smallest in size. Water comes in from Lake Erie via the Niagara River (and Niagara Falls) and leaves via the Saint Lawrence River, headed for the Atlantic Ocean.

Although the Lake Ontario shore is heavily populated and developed in Canada, the American shore tends to be undeveloped and rural.

Nearby destinations

Lake Ontario is shared by the Canadian province of Ontario and the U.S. state of New York. The largest city on the American side is Rochester; the largest on the Canadian side is Toronto. Both countries' cities of Niagara Falls are nearby. The Thousand Islands region lies at the lake's outlet.

American destinations worth visiting along the lakeshore include the historic village of Sackets Harbor, the city of Oswego (particularly during its large Harborfest celebration each summer, renowned for its fireworks display), and state beaches such as Fair Haven, Hamlin, Southwick or Westcott. A long-running Renaissance Fair takes place in Sterling during July and August.

The region includes:

• Ontario — Much of Central Ontario and part of Eastern Ontario, Canada including Toronto-Hamilton, Cobourg, Trenton-Belleville, Prince Edward County and Kingston. This region includes Niagara Falls and a substantial section of the Windsor-Quebec corridor.
• New York State — Portions of Western New York and Northern New York in the United States of America, including Niagara Falls, Rochester and Oswego.