Denmark is an unincorporated community in northeastern Lee County, Iowa, United States. It lies along Iowa Highway 16 north of the city of Fort Madison, the county seat of Lee County. Its elevation is 722 feet (220 m). Although Denmark is unincorporated, it has a post office, with the ZIP code of 52624, which opened on 1846-04-07. The community is part of the Fort Madison–Keokuk, IA-MO Micropolitan Statistical Area.