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.

According to the U.S. Census Bureau, the county has a total area of 766 square miles (1,980 km), of which 720 square miles (1,900 km) is land and 46 square miles (120 km) (6.0%) is water.

• Winnebago County – north
• Calumet County – northeast
• Sheboygan County – east
• Washington County – southeast
• Dodge County – southwest
• Green Lake County – west

• Horicon National Wildlife Refuge (part)

• Canadian National
• Wisconsin and Southern Railroad

• Fond du Lac Area Transit

Fond du Lac County Airport (IATA: FLD, ICAO: KFLD, FAA LID: FLD) serves the county and surrounding communities.

Fond du Lac County Climate chart (explanation) J F M A M J J A S O N D     73     −8 −12     68     −7 −13     85     4 −6     151     17 2     126     23 6     142     25 14     94     28 16     90     24 14     80     22 11     125     15 7     65     5 −2     70     −3 −10 █ Average max. and min. temperatures in °C █ Precipitation totals in mm Source: Imperial conversion J F M A M J J A S O N D     2.9     18 10     2.7     19 9     3.3     39 21     5.9     63 36     5     73 43     5.6     77 57     3.7     82 61     3.5     75 57     3.1     72 52     4.9     59 45     2.6     41 28     2.8     27 14 █ Average max. and min. temperatures in °F █ Precipitation totals in inches

Historical population

Census	Pop.	Note	%±
1840	139		—
1850	14,510		10,338.8%
1860	34,154		135.4%
1870	46,273		35.5%
1880	46,859		1.3%
1890	44,088		−5.9%
1900	47,589		7.9%
1910	51,610		8.4%
1920	56,119		8.7%
1930	59,883		6.7%
1940	62,353		4.1%
1950	67,829		8.8%
1960	75,085		10.7%
1970	84,567		12.6%
1980	88,964		5.2%
1990	90,083		1.3%
2000	97,296		8.0%
2010	101,633		4.5%
2020	104,154		2.5%
U.S. Decennial Census 1790–1960 1900–1990 1990–2000 2010–2020

As of the census of 2020, the population was 104,154. The population density was 144.7 inhabitants per square mile (55.9/km). There were 45,740 housing units at an average density of 63.6 units per square mile (24.6 units/km). The racial makeup of the county was 88.0% White, 2.3% Black or African American, 1.2% Asian, 0.5% Native American, 3.0% from other races, and 5.0% from two or more races. Ethnically, the population was 6.4% Hispanic or Latino of any race.

As of the census of 2000, there were 97,296 people, 36,931 households, and 25,482 families residing in the county. The population density was 135 people per square mile (52 people/km). There were 39,271 housing units at an average density of 54 units per square mile (21 units/km). The racial makeup of the county was 96.16% White, 0.90% Black or African American, 0.38% Native American, 0.87% Asian, 0.03% Pacific Islander, 0.84% from other races, and 0.82% from two or more races. 2.04% of the population were Hispanic or Latino of any race. 57.7% were of German, 6.1% Irish and 5.3% American ancestry. 95.5% spoke English, 2.1% Spanish and 1.3% German as their first language.

There were 36,931 households, out of which 32.80% had children under the age of 18 living with them, 57.70% were married couples living together, 7.80% had a female householder with no husband present, and 31.00% were non-families. 25.40% of all households were made up of individuals, and 10.80% had someone living alone who was 65 years of age or older. The average household size was 2.52 and the average family size was 3.04.

In the county, the population was spread out, with 25.20% under the age of 18, 9.40% from 18 to 24, 28.70% from 25 to 44, 22.40% from 45 to 64, and 14.30% who were 65 years of age or older. The median age was 37 years. For every 100 females there were 95.30 males. For every 100 females age 18 and over, there were 92.20 males.

In 2017, there were 1,066 births, giving a general fertility rate of 57.7 births per 1000 women aged 15–44, the 20th lowest rate out of all 72 Wisconsin counties. Additionally, there were 74 reported induced abortions performed on women of Fond du Lac County residence in 2017.

• Fond du Lac (county seat)
• Ripon
• Waupun (mostly in Dodge County)

• St. Peter
• Taycheedah
• Van Dyne

• Ceresco
• New Cassel
• Reeds Corners

• Campbellsport High School
• Fond Du Lac High School
• Horace Mann High School
• Ripon High School

United States presidential election results for Fond du Lac County, Wisconsin

Year	Republican		Democratic		Third party(ies)
	No.	%	No.	%	No.	%
2024	37,272	63.68%	20,495	35.02%	760	1.30%
2020	35,754	62.45%	20,588	35.96%	909	1.59%
2016	31,022	59.89%	17,387	33.57%	3,387	6.54%
2012	30,355	56.84%	22,379	41.91%	668	1.25%
2008	28,164	53.83%	23,463	44.84%	696	1.33%
2004	33,291	62.77%	19,216	36.23%	529	1.00%
2000	26,548	56.98%	18,181	39.02%	1,860	3.99%
1996	16,488	44.65%	15,542	42.08%	4,901	13.27%
1992	19,785	44.45%	13,757	30.91%	10,964	24.63%
1988	21,985	57.59%	15,887	41.62%	303	0.79%
1984	26,069	64.61%	13,983	34.66%	294	0.73%
1980	24,196	56.97%	15,293	36.01%	2,981	7.02%
1976	22,226	55.79%	16,571	41.59%	1,044	2.62%
1972	21,007	60.99%	12,050	34.99%	1,386	4.02%
1968	18,184	55.59%	12,563	38.41%	1,962	6.00%
1964	12,708	41.29%	18,040	58.61%	30	0.10%
1960	19,498	59.65%	13,132	40.17%	58	0.18%
1956	21,496	72.46%	7,940	26.76%	230	0.78%
1952	22,794	74.43%	7,724	25.22%	107	0.35%
1948	13,760	59.61%	8,904	38.57%	419	1.82%
1944	16,785	63.81%	9,378	35.65%	143	0.54%
1940	16,804	61.46%	10,323	37.76%	215	0.79%
1936	9,179	35.40%	14,821	57.16%	1,931	7.45%
1932	8,436	33.74%	16,143	64.56%	425	1.70%
1928	12,593	51.36%	11,719	47.80%	205	0.84%
1924	8,516	41.62%	2,222	10.86%	9,722	47.52%
1920	12,543	74.58%	3,409	20.27%	867	5.15%
1916	5,781	52.16%	5,021	45.30%	282	2.54%
1912	3,014	31.34%	4,838	50.31%	1,764	18.34%
1908	5,872	50.86%	5,194	44.99%	479	4.15%
1904	7,027	59.58%	4,417	37.45%	350	2.97%
1900	6,258	53.82%	5,140	44.20%	230	1.98%
1896	6,174	54.15%	4,933	43.27%	294	2.58%
1892	4,129	42.47%	5,254	54.04%	339	3.49%

Fond du Lac has been a historically Republican county, as the party was founded in the town of Ripon, located within the county. It has only voted Democratic in the national landslides of 1964, 1936, and 1932, as well as from 1872 to 1892.

• National Register of Historic Places listings in Fond du Lac County, Wisconsin
• Wisconsin Phalanx

• Glaze, A. T. Incidents and Anecdotes of Early Days and History of Business in the City and County of Fond du Lac From Early Times to the Present. Fond du Lac: P. B. Haber, 1905.
• McKenna, Maurice (ed.). Fond du Lac County Wisconsin, Past and Present. Chicago: S. J. Clarke, 1912.

• Fond du Lac County website
• Fond du Lac County map from the Wisconsin Department of Transportation