Sault Ste. Marie is a city in Ontario, Canada. The third-largest city in Northern Ontario after Sudbury and Thunder Bay, it is located on the St. Mary's River on the Canada–US border. To the southwest, across the river, is the United States and the city of Sault Ste. Marie, Michigan. The two cities are joined by the Sault Ste. Marie International Bridge, which connects Interstate 75 on the Michigan side to Huron Street on the Ontario side.