Grosse Ile is an American island in Wayne County in the U.S. state of Michigan. Located just west of the Canada–United States border in the Detroit River, it is the largest island in the river and the most-populated island in the state of Michigan. The island is administered by Grosse Ile Township.

Wayne County is the most populous county in the U.S. state of Michigan. As of 2020, the United States Census placed its population at 1,793,561, making it the 19th-most populous county in the United States. The county seat is Detroit. The county was founded in 1796 and organized in 1815. Wayne County is included in the Detroit-Warren-Dearborn, MI Metropolitan Statistical Area. It is one of several U.S. counties named after Revolutionary War-era general Anthony Wayne.