Muskegon Lake is a 4,150-acre (16.8 km2) fresh-water lake in Muskegon County, Michigan, USA. Located in the lower peninsula at the mouth of the Muskegon River, Muskegon Lake forms a 12-square-mile (31 km2) broad harbor along the eastern shoreline of Lake Michigan, approximately 2.5 miles (4.0 km) wide by 5.5 miles (8.9 km) long.