French Island is a census-designated place in La Crosse County, Wisconsin, United States. The population was 4,207 at the 2010 census. It lies on an island of the same name, though they are not coextensive; a portion of the island is part of the city of La Crosse. All of the island is part of the La Crosse Metropolitan Statistical Area. French Island is part of the town of Campbell and contains all of its population, because the balance of Campbell is uninhabited.