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is a civil township of Wayne County in the U.S. state of Michigan. The township is coterminous with the island in the Detroit River called
. The name comes from French, meaning "Big Island". The population was 10,894 at the 2000 census.
According to the United States Census Bureau, the township has a total area of 18.3 square miles (47.5 km²), of which 9.6 square miles (24.9 km²) of it (52.6%) is land and 8.7 square miles (22.6 km²) of it (47.4%) is water.
Grosse Ile is the largest island on the Detroit River. Grosse Ile is actually composed of twelve islands although the community is most often identified with the "main island" (which residents simply refer to as "The Island"). Grosse Ile's "main island" is technically composed of two islands.
The tip of the "main island's" northern section is named Hennepen Point in honor of the 17th Century French explorer Father Louis Hennepin. It is uninhabited and separated from the remainder of the northern section by an unnamed canal that cannot be navigated in a power boat.
The southern section of the "main island" is separated from the northern section by the Thorofare Canal which runs on a diagonal course from east to west connecting the main channel of the Detroit River with the Trenton Channel of the river. The southern section of the "main island" is connected by bridges to Elba Island, Upper Hickory Island (also known as Meso), Hickory Island, and Swan Island which are all inhabited.
In addition, not far from the shoreline of the "main island" in the river lie Calf Island, Celeron Island (charted as Tawas Island), Dynamite (also known as Powder House Island), Fox Island, Stony Island, and Sugar Island which are all uninhabited. Stony and Celeron are owned by the Michigan Department of Natural Resources. Calf Island is owned by the U.S. Fish and Wildlife Service as a part of the Detroit River International Wildlife Refuge . The other islands are privately owned.
Two bridges connect the "main island" to the mainland of Michigan. The bridge on the north end of the island is called the Grosse Ile Toll Bridge (off-white color). The bridge on the south end of the island is officially named the Wayne County Bridge (light green in color), but is commonly called the "Free Bridge" by locals.
The Wayne County Bridge was closed for major renovation between May 2, 2007 and December 21, 2007. While the county bridge was closed, all traffic traveled over the Toll Bridge.
Although Grosse Ile is technically located "downriver," it is markedly different than surrounding communities.