Arenac County (/ˈɛərənæk/ AIR-ə-nak) is a county located in the U.S. state of Michigan. As of the 2020 Census, the population was 15,002. The county seat is Standish.

Arenac County was created by the Michigan Territory on 2 March 1831, then attached on 2 March 1836 to Saginaw County for administration. The creation and organization of Bay County overlaid Arenac and annexed portions of Saginaw and Midland Counties, causing the legal elimination of Arenac County on 20 April 1857. On 21 April 1883 Arenac County was re-created from the then existing northern townships of Bay County, with somewhat different boundaries than its previous creation. The name Arenac, coined by Henry Rowe Schoolcraft, a US Indian Agent and ethnologist, is a derivation of the Latin arena and the Native American ac. The combined words mean “A sandy place for a good footing.”

The county includes some off-reservation trust lands held by the federal government for the federally recognized Saginaw Chippewa Tribal Nation, which is based in Isabella County. In early 2007, plans were confirmed for a casino to be constructed outside of the city of Standish with a scheduled opening by the end of the year. It is owned and operated by the Saginaw Chippewa Tribe. The Saganing Eagles Landing Casino grand opening was held on January 24, 2008.

According to the U.S. Census Bureau, the county has a total area of 681 square miles (1,760 km), of which 363 square miles (940 km) is land and 317 square miles (820 km) (47%) is water. It is the third-smallest county in Michigan by land area. Arenac County can be considered a part of either Northern Michigan or Central Michigan.

• Saginaw Bay on Lake Huron
• Au Gres River
• Rifle River
• Pine River (Arenac County)

• I-75
• US 23
• M-13
• M-33
• M-61
• M-65

By land

• Iosco County (northeast)
• Bay County (south)
• Gladwin County (west)
• Ogemaw County (northwest)

By water

• Tuscola County (south)
• Huron County (southeast)

• Michigan Islands National Wildlife Refuge (part)

Historical population

Census	Pop.	Note	%±
1890	5,683		—
1900	9,821		72.8%
1910	9,640		−1.8%
1920	9,460		−1.9%
1930	8,007		−15.4%
1940	9,233		15.3%
1950	9,644		4.5%
1960	9,860		2.2%
1970	11,149		13.1%
1980	14,706		31.9%
1990	14,931		1.5%
2000	17,269		15.7%
2010	15,899		−7.9%
2020	15,002		−5.6%
2023 (est.)	15,145		1.0%
US Decennial Census 1790-1960 1900-1990 1990-2000 2010-2018

As of the 2000 United States Census, there were 17,269 people, 6,710 households, and 4,717 families in the county. The population density was 47 people per square mile (18 people/km). There were 9,563 housing units at an average density of 26 per square mile (10/km). The racial makeup of the county was 95.38% White, 1.82% Black or African American, 0.95% Native American, 0.29% Asian, 0.01% Pacific Islander, 0.21% from other races, and 1.33% from two or more races. 1.38% of the population were Hispanic or Latino of any race. 24.0% were of German, 14.1% Polish, 11.6% French, 10.6% American, 7.9% English, 6.8% Irish and 5.3% French Canadian ancestry. 96.9% spoke English and 1.3% Spanish as their first language.

There were 6,710 households, out of which 29.00% had children under the age of 18 living with them, 57.00% were married couples living together, 9.00% had a female householder with no husband present, and 29.70% were non-families. 25.50% of all households were made up of individuals, and 12.30% had someone living alone who was 65 years of age or older. The average household size was 2.45 and the average family size was 2.92.

The county population contained 23.30% under the age of 18, 7.80% from 18 to 24, 26.80% from 25 to 44, 25.50% from 45 to 64, and 16.60% who were 65 years of age or older. The median age was 40 years. For every 100 females there were 105.40 males. For every 100 females age 18 and over, there were 104.40 males.

The median income for a household in the county was $32,805, and the median income for a family was $39,033. Males had a median income of $31,205 versus $20,363 for females. The per capita income for the county was $16,300. About 11.30% of families and 13.90% of the population were below the poverty line, including 20.70% of those under age 18 and 7.80% of those age 65 or over.

• The Roman Catholic Diocese of Saginaw is the controlling regional body for the Catholic Church.
• There are no meetinghouses of the Church of Jesus Christ of Latter-day Saints located within Arenac County.

Arenac County could be described as slightly Republican-leaning. Since 1884, the Republican Party nominee has carried the county vote in 56% of the elections (20 of 36 elections). Due to 4 elections won by independent candidates during that period, the Democratic record is only 33% (12 of 36).

In 2024, Donald Trump won nearly 70% of the vote in Arenac County, the largest vote share any candidate has received in the county's history.

United States presidential election results for Arenac County, Michigan

Year	Republican		Democratic		Third party(ies)
	No.	%	No.	%	No.	%
2024	6,379	69.62%	2,662	29.05%	122	1.33%
2020	5,928	67.07%	2,774	31.38%	137	1.55%
2016	4,950	64.04%	2,384	30.84%	395	5.11%
2012	4,057	51.74%	3,669	46.79%	115	1.47%
2008	3,807	46.84%	4,155	51.12%	166	2.04%
2004	4,071	49.55%	4,076	49.61%	69	0.84%
2000	3,421	47.08%	3,685	50.71%	161	2.22%
1996	2,247	34.09%	3,472	52.68%	872	13.23%
1992	2,330	32.33%	3,244	45.02%	1,632	22.65%
1988	3,064	48.63%	3,211	50.97%	25	0.40%
1984	3,483	58.63%	2,436	41.00%	22	0.37%
1980	3,436	53.43%	2,547	39.61%	448	6.97%
1976	2,687	49.55%	2,695	49.70%	41	0.76%
1972	2,588	57.43%	1,829	40.59%	89	1.98%
1968	2,089	52.37%	1,573	39.43%	327	8.20%
1964	1,413	36.68%	2,436	63.24%	3	0.08%
1960	2,352	55.34%	1,888	44.42%	10	0.24%
1956	2,631	63.32%	1,520	36.58%	4	0.10%
1952	2,753	67.74%	1,290	31.74%	21	0.52%
1948	1,790	58.86%	1,203	39.56%	48	1.58%
1944	1,978	60.47%	1,280	39.13%	13	0.40%
1940	2,293	60.23%	1,499	39.37%	15	0.39%
1936	1,505	43.50%	1,761	50.90%	194	5.61%
1932	1,471	40.13%	2,086	56.90%	109	2.97%
1928	1,612	67.87%	749	31.54%	14	0.59%
1924	1,767	67.57%	575	21.99%	273	10.44%
1920	1,521	66.36%	669	29.19%	102	4.45%
1916	911	46.86%	938	48.25%	95	4.89%
1912	421	21.17%	452	22.72%	1,116	56.11%
1908	1,081	56.19%	714	37.11%	129	6.70%
1904	1,372	68.77%	458	22.96%	165	8.27%
1900	972	51.02%	861	45.20%	72	3.78%
1896	611	37.39%	997	61.02%	26	1.59%
1892	322	27.81%	373	32.21%	463	39.98%
1888	357	31.85%	261	23.28%	503	44.87%
1884	323	35.57%	17	1.87%	568	62.56%

The county government operates the jail, maintains rural roads, operates the major local courts, records deeds, mortgages, and vital records, administers public health regulations, and participates with the state in the provision of social services. The county board of commissioners controls the budget and has limited authority to make laws or ordinances. In Michigan, most local government functions — police and fire, building and zoning, tax assessment, street maintenance, etc. — are the responsibility of individual cities and townships.

(information as of March 2009)

• Au Gres
• Omer
• Standish (county seat)

• Sterling
• Turner
• Twining

• Alger
• Delano
• Maple Ridge
• Melita
• Pine River

• Arenac County contains off-reservation trust land belonging to the Isabella Indian Reservation. They occupy three small parcels of land located within Standish Township.

• Sunrise Side Heritage Bike Ride, first weekend in September. Ride Along Lake Huron Shoreline (US 23) from the Arenac County fairgrounds to Mackinac Bridge then South to West Branch on M-33 and M-55 . This is a 400-mile long organized ride.

• List of Michigan State Historic Sites in Arenac County, Michigan
• National Register of Historic Places listings in Arenac County, Michigan
• USS Arenac (APA-128)

• Romig, Walter (1986) [1973]. Michigan Place Names: The History of the Founding and the Naming of More than Five Thousand Past and Present Michigan Communities. Great Lakes Books. Detroit: Wayne State University Press. ISBN 978-0814318386.

• The Arenac County Independent
• Arenac County government
• "Bibliography on Arenac County". Clarke Historical Library, Central Michigan University.

44°03′N 83°45′W / 44.05°N 83.75°W / 44.05; -83.75