Fort Madison is a city in Lee County, Iowa, United States, serving as one of the county's two county seats alongside Keokuk. It is situated in the state's southeast corner along the Mississippi River, positioned between small bluffs near one of the river's widest portions. The city occupies a total area of 13.23 square miles, with land comprising 9.49 square miles and water covering 3.74 square miles.

The city was established around the site of the historic Fort Madison (1808–1813), the first permanent U.S. military fortification on the Upper Mississippi. Built to control trade and pacify Native Americans, the fort was abandoned and burned in September 1813 after intense sieges. The town of Fort Madison was laid out in 1835 by General John Holly Knapp and Nathaniel Knapp, relocating in 1840 due to land title issues.

Notable landmarks include the Iowa State Penitentiary, a replica of the original fort, and the Fort Madison Toll Bridge, one of two remaining double swing-span bridges on the Mississippi River. The city features the Fort Madison Downtown Commercial Historic District with late 19th-century storefronts and the Park-to-Park Residential Historic District, which contains homes in Gothic, Victorian, and Tudor styles listed on the National Historic Registry.

Fort Madison hosts several annual events including the Tri-State Rodeo, RiverFest, Mexican Fiesta, Balloons Over the Mississippi, Art in Central Park, and an Annual Lighted Parade. The city is also known for Sheaffer Pens, which were developed and manufactured there for many years. Preservation efforts continue for the original fort site, where archaeological excavations have exposed the central blockhouse and officers' quarters foundations.

The population was 10,270 as of the 2020 census, with 98.1% of residents living in urban areas. Amtrak's Southwest Chief makes its only Iowa stop here, providing rail access between Chicago and Los Angeles. The city also has a municipal airport for general aviation. While specific climate data is not detailed, the location along the river influences local weather patterns.