Navy Island is a small, uninhabited island in the Niagara River in the province of Ontario, managed by Parks Canada as a National Historic Site of Canada. It is located about 4.5 km (2.8 mi) upstream from Horseshoe Falls, and has an area of roughly 1.2 km² (0.46 sq mi). It was designated a national historic site in 1921 in recognition of its role in shipbuilding and the location of the short–lived Republic of Canada.