Rideau Lakes, 65 km2, elev 123 m, mean depth 12.3 m, is a commonly used collective name for 3 lakes: Big Rideau, Upper Rideau and Lower Rideau. They are located near the height of land on the Rideau Canal system between Kingston and Ottawa in eastern Ontario. Their natural drainage is to the NE, by way of the Rideau R through the town of Smiths Falls.
Located on the Frontenac axis of the Canadian Shield, the lakes are studded with islands and their surrounding shores are rocky. They are used almost entirely for recreational activities such as boating and cottaging; their common sport fish are largemouth and smallmouth bass, northern pike, lake trout and yellow perch. The waterway through these lakes was originally an Indian canoe route. The intent of making it navigable for larger craft was strategic. Col By built the canal 1826-32, primarily to provide access from Montréal to Kingston for troops and supplies, along a route that would be free of risk from American attack. The name of the lakes is derived from a waterfall at the mouth of the Rideau R that early French explorers named for its resemblance to a curtain.