Fond du Lac County is a county in the U.S. state of Wisconsin. As of the 2020 census, the population was 104,154. Its county seat is Fond du Lac. The county was created in the Wisconsin Territory in 1836 and later organized in 1844. Fond du Lac is French for "bottom of the lake", given so because of the county's location at the southern shore of Lake Winnebago. Fond du Lac County comprises the Fond du Lac, Wisconsin Metropolitan Statistical Area. The Holyland region is in northeastern Fond du Lac County.

Fond du Lac is a city in and the county seat of Fond du Lac County, Wisconsin, United States. 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. Fond du Lac is the 348th-largest metropolitan area in the United States.