Detroit River, a short river that forms part of the boundary between Michigan and Ontario. It is one of the world's busiest inland waterways, being part of the navigation link between Lakes Huron and Erie in the Great Lakes–St. Lawrence Seaway system. The river flows southwest and south from Lake St. Clair to Lake Erie and is about 30 miles (48 km) long. Detroit (Michigan) and Windsor (Ontario) lie on its banks; they are linked by two tunnels and a suspension bridge.