Winnebago County is a county in the U.S. state of Wisconsin. As of the 2020 census, the population was 171,730. Its county seat is Oshkosh. It was named for the historic Winnebago people, a federally recognized Native American tribe now known as the Ho-Chunk Nation. Chief Oshkosh was a Menominee leader in the area. Winnebago County comprises the Oshkosh-Neenah, WI Metropolitan Statistical Area, which is included in the Appleton-Oshkosh-Neenah, WI Combined Statistical Area.

Oshkosh is a city in and the county seat of Winnebago County, Wisconsin, United States. The city had a population of 66,816 in 2020, making it the ninth-most populous city in Wisconsin. It is also adjacent to the much less populous Town of Oshkosh in the north.