The United Counties of Stormont, Dundas and Glengarry (SDG) is an upper-tier municipality in the Canadian province of Ontario that comprises three historical counties and excludes the City of Cornwall and the Mohawk Nation of Akwesasne. However, both Cornwall and Akwesasne form part of a larger census division named for the United Counties of Stormont, Dundas and Glengarry. The municipality's administrative office is located within Cornwall.

Cornwall is a city in Eastern Ontario, Canada, situated where the provinces of Ontario and Quebec and the state of New York converge. It is the seat of the United Counties of Stormont, Dundas, and Glengarry and is Ontario's easternmost city.