The Detroit River is a 28.0-mile-long (45.1 km)strait in the Great Lakes system. The name comes from the French Rivière du Détroit, which translates literally as "River of the Strait". The Detroit River has served an important role in the history of Detroit and is one of the busiest waterways in the world. The river travels south from Lake St. Clair to Lake Erie, and the whole river carries the international border between Canada and the United States. The river divides the major metropolitan areas of Detroit, Michigan, and Windsor, Ontario — an area referred to as Detroit–Windsor. The two are connected by the Ambassador Bridge and the Detroit–Windsor Tunnel.

The river serves as an important transportation route connecting Lake Michigan, Huron, and Superior to the St. Lawrence Seaway and Erie Canal. When Detroit underwent rapid industrialization at the turn of the 20th century, the Detroit River became notoriously polluted and toxic. In recent years, however, the ecological importance of the river has warranted a vast restoration effort, and the river today has a wide variety of economical and recreational uses. There are numerous islands in the Detroit River, and much of the lower portion of the river is incorporated into the Detroit River International Wildlife Refuge. The portion of the river in the city of Detroit has been organized into the Detroit International Riverfront and the William G. Milliken State Park and Harbor. The Detroit River is designated an American Heritage River and a Canadian Heritage River — the only river to have this dual designation.

Detroit ( /diˈtrɔɪt/) is the largest city in the U.S. state of Michigan, and the seat of Wayne County. It is the major city among the primary cultural, financial, and transportation centers in the Metro Detroit area, a region of 5.2 million people, and serves as a major port on the Detroit River connecting the Great Lakes system to the Saint Lawrence Seaway. It was founded on July 24, 1701, by the French explorer, adventurer, and nobleman Antoine de la Mothe, sieur de Cadillac.

In 2010, the city had a population of 713,777 and ranked as the 18th most populous city in the United States. The name Detroit sometimes refers to the Metro Detroit area with a population of 4,296,250 for the six-county Metropolitan Statistical Area, the United States' eleventh-largest, and a population of 5,218,852 for the nine-county Combined Statistical Area as of the 2010 Census. The Detroit–Windsor area, a critical commercial link straddling the Canada–U.S. border, has a total population of about 5,700,000.

Known as the world's traditional automotive center, "Detroit" is a metonym for the American automobile industry and an important source of popular music legacies celebrated by the city's two familiar nicknames, the Motor City and Motown. Other nicknames arose in the 20th century, including City of Champions beginning in the 1930s for its successes in individual and team sport,The D, D-Town, Hockeytown (a trademark owned by the city's NHL club, the Red Wings), Rock City (after the Kiss song "Detroit Rock City"), and The 313 (its telephone area code) Detroit became known as the "great arsenal of democracy" for its support of the U.S. role among the Allied powers during World War II.