Niagara-on-the-Lake is a Canadian town in Southern Ontario located on Lake Ontario at the mouth of the Niagara River.

It was incorporated 1792 as the Town of Newark and was named the capital of the Province of Upper Canada. The town was renamed Niagara in 1798. The present name Niagara-on-the-Lake was adopted in 1880 to distinguish it from the Canadian and U.S. cities of Niagara Falls but it was officially adopted only in 1970 after the merger of Town of Niagara and the Township of Niagara.

The town has a total area of 132.83 km2 (51.3 sq mi) with a total population of 14,587 as of 2006.

A popular tourist destination, the town is an architectural and historical treasure, with many well-preserved 19th-century buildings.

It is the site for the annual Shaw Festival, a series of theatrical productions featuring the works of George Bernard Shaw, his contemporaries, or plays about his era (1856-1950), running from April to November.

Rich with British heritage, the town features the only Lord Mayor, as head of the town government, in Canada.