Denison is a city in Crawford County, Iowa, United States, along the Boyer River. The population was 7,339 at the 2000 census. It is the county seat of Crawford County.
Denison is located at 42°1′2″N 95°21′4″W / 42.01722°N 95.35111°W / 42.01722; -95.35111 (42.017187, -95.351124).
According to the United States Census Bureau, the city has a total area of 6.2 square miles (16.1 km²), of which, 6.2 square miles (16.0 km²) of it is land and 0.04 square miles (0.1 km²) of it (0.48%) is water.