The Rideau Canal (French: Canal Rideau), also known as the Rideau Waterway, connects the city of Ottawa, Ontario, Canada, on the Ottawa River to the city of Kingston, Ontario, on Lake Ontario. The canal was opened in 1832 as a precaution in case of war with the United States and is still in use today, with most of its original structures intact. The canal system uses sections of major rivers, including the Rideau and the Cataraqui, as well as some lakes. It is the oldest continuously operated canal system in North America, and in 2007 it was registered as a UNESCO World Heritage Site.

It is operated today by Parks Canada as a recreational waterway. The locks on the system open for navigation in mid-May and close in mid-October.

The construction of the Rideau Canal was a preventive military measure undertaken after a report that during the War of 1812 the United States had intended to invade the British colony of Upper Canada via the St. Lawrence, which would have severed the lifeline between Montreal and Kingston. The British built a number of other canals (Grenville, Chute-à-Blondeau and Carillon Canals, all along the Ottawa River) as well as a number of forts (Citadel Hill, La Citadelle, and Fort Henry) to impede and deter any future American invasions of Canadian territory.