Koshkonong is a town in Jefferson County, Wisconsin, United States. The population was 3,763 at the 2020 census. The town entirely surrounds the city of Fort Atkinson. The unincorporated communities of Koshkonong Mounds and Vinnie Ha Ha are located in the town. The unincorporated communities of Blackhawk Island and Koshkonong, as well as The Census-designated place of Lake Koshkonong are also located partially in the town.

Jefferson County is a county in the U.S. state of Wisconsin. As of the 2020 census, the population was 84,900. Its county seat is Jefferson. Jefferson County comprises the Watertown-Fort Atkinson, WI Micropolitan Statistical Area, which is also included in the Milwaukee-Racine-Waukesha, WI Combined Statistical Area.