Brockville, in the past Elizabethtown, is a city in Eastern Ontario, Canada in the Thousand Islands locale. Despite the fact that it is the seat of the United Counties of Leeds and Grenville, it is politically autonomous of the district. It is incorporated with Leeds and Grenville for statistics purposes as it were.

Known as the "City of the 1000 Islands", Brockville is on the north shore of the Saint Lawrence River inverse Morristown, New York, about somewhere between Ontario's Cornwall toward the east and Kingston toward the west.