Koshkonong is a town in Jefferson County, Wisconsin, United States. The population was 3,692 at the 2010 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.