Fond du Lac is a city in Fond du Lac County, Wisconsin, United States, and its county seat. It is located at the southern end of Lake Winneba…Fond du Lac is a city in Fond du Lac County, Wisconsin, United States, and its county seat. It is located at the southern end of Lake Winnebago and had a population of 44,678 at the 2020 census. The city forms the core of the Fond du Lac metropolitan statistical area, which includes all of Fond du Lac County and had 104,154 residents in 2020.