Fond du Lac is a city in and the county seat of Fond du Lac County, Wisconsin, United States, located at the southern end of Lake Winne…Fond du Lac is a city in and the county seat of Fond du Lac County, Wisconsin, United States, located at the southern end of Lake Winnebago. The population was 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.