Rideau Lakes is a township located within Leeds and Grenville United Counties in Eastern Ontario, Canada. The township was incorporated on 1 January 1998 by amalgamating the former townships of North Crosby, South Crosby, Bastard, South Burgess and South Elmsley with the village of Newboro. Rideau Lakes lies in the northwest corner of Leeds and Grenville, and is geographically the largest municipality in the county.