The Straits of Mackinac (/ˈmækᵻnɔː/ MAK-in-aw) is a narrow waterway in the U.S. state of Michigan, between Michigan's Lower and Upper Peninsulas. The Straits of Mackinac connect two of the Great Lakes, Lake Michigan and Lake Huron. The straits are five miles (8.0 km) wide and 20 fathoms (120 ft; 37 m) deep. Hydrologically, the two connected lakes can be considered one, which is called Lake Michigan–Huron. Historically, the region around the Straits was known by the native Odawa people as Michilimackinac. The Straits of Mackinac is "whipsawed by currents unlike anywhere else in the Great Lakes."
The Straits of Mackinac is a major shipping lane, providing passage for raw materials and finished goods and connecting, for instance, the iron mines of Minnesota to the steel mills of Gary, Indiana. Before the railroads reached Chicago from the east, most immigrants arrived in the Midwest and Great Plains by ships on the Great Lakes. The straits is five miles (8 km) wide at its narrowest point, where it is spanned by the Mackinac Bridge. Before the bridge was built, car ferries transported vehicles across the straits. Today passenger-only ferries carry people to Mackinac Island, which does not permit cars. Visitors can take their vehicles on a car ferry to Bois Blanc Island.