Denmark is an unincorporated community and census-designated place in northeastern Lee County, Iowa, United States. It lies along Iowa Highway 16, north of the city of Fort Madison, the county chair of Lee County. Its height is 722 feet (220 m) above sea level. Although Denmark is unincorporated, it has a publish office in the same way as the ZIP code of 52624, that opened upon April 7, 1846. The town as well as has a branch of Farmers Savings Bank that opened in 1935. The community is part of the Fort Madison–Keokuk, IA-MO Micropolitan Statistical Area. As of the 2020 census, its population was 425.

Denmark was laid out circa 1837.

In 1836, four families emigrated from the town and church of New Ipswich, NH to Denmark in what was then Wisconsin Territory, now in Iowa. Within a gruff time they were followed by eight other families. They all carried subsequent to them the thesame standard of right perky and wise planning for the best fascination of those who should come after them that they had known in New Ipswich. Those who “laid out the town of Denmark, which is three-fourths of a mile square, into town lots for building, donated one-half of those lots to the endeavor of Education.” In the building of a church and of an academy they followed as contiguously as possible the example set by the founders of New Ipswich. The church set taking place by the settlers is the oldest Congregational church in Iowa. They were prematurely known as champions of freedom. “Under the leadership of their pastor, Rev. Asa Turner, they allied with others in the election of Governor Grimes in 1854, which distorted the embassy history of Iowa and gave birth to the Republican party in the nation.” Dr. Turner and Rev. Mr. Lee were classmates at Yale College and lifelong friends. His pastorate continued for thirty years; and his influence led to Iowa the eleven youngster men from Andover Seminary who formed the “Iowa Band,” one of whom, their historian, was Rev. Ephraim Adams, a son of New Ipswich.

The Fort Madison Community School District serves Denmark, operating Lincoln and Richardson elementary schools, Fort Madison Middle School, and Fort Madison High School.