Fort Winnebago was a 19th-century fortification of the United States Army located on a hill overlooking the eastern end of the portage between the Fox and Wisconsin Rivers east of present-day Portage, Wisconsin. It was the middle one of three fortifications along the Fox-Wisconsin Waterway that also included Fort Howard in Green Bay, Wisconsin and Fort Crawford in Prairie du Chien, Wisconsin. Fort Winnebago was constructed in 1828 as part of an effort to maintain peace between white settlers and the region's Native American tribes following the Winnebago War of 1827. The fort's location was chosen not only because of its proximity to the site of Red Bird's surrender in the Winnebago War, but also because of the strategic importance of the portage on the Fox-Wisconsin Waterway, a heavily traveled connection between the Great Lakes and the Mississippi River. Fort Winnebago's location near the portage allowed it to regulate transportation between the lakes and the Mississippi.

Portage is a city in and the county seat of Columbia County, Wisconsin, United States. The population was 10,581 at the 2020 census, making it the largest city in Columbia County. The city is part of the Madison Metropolitan Statistical Area.