{{Stack|[[Image:USA Fentress County, Tennessee.csv age pyramid.svg|thumb|left|150px|Age pyramid Fentress County<ref>Based on [[2000 United States Census|2000 census]] data</ref>]]}}
As of the 2010 [[census]],<ref>{{cite web|url=http://factfinder2factfinder.census.gov|archive-url=https://archive.today/20200212221153/http://factfinder.census.gov/main.html|url-status=dead|archive-date=February 12, 2020|publisher=[[United States Census Bureau]]|accessdate=May 14, 2011|title=American FactFinder|url-status=dead|archiveurl=https://web.archive.org/web/20130911234518/http://factfinder2.census.gov/|archivedate=September 11, 2013}}</ref> there were 17,959 people, 7,326 households, and 4,818 families residing in the county. The [[population density]] was 36 people per square mile (13/km²). There were 8,927 housing units at an average density of 15 per square mile (6/km²). The racial makeup of the county was 98.1% [[Race (United States Census)|White]], 0.2% [[Race (United States Census)|Black]] or [[Race (United States Census)|African American]], 0.2% [[Race (United States Census)|Native American]], 0.2% [[Race (United States Census)|Asian]], 0.4% from [[Race (United States Census)|other races]], and 0.9% from two or more races. 1.1% of the population were [[Race (United States Census)|Hispanic]] or [[Race (United States Census)|Latino]] of any race.
In the county's 7,326 households, 23.1% had children under the age of 18, 57.30% were [[Marriage|married couples]] living together, 11.30% had a female householder with no husband present, and 28.00% were non-families. 25.50% of all households were made up of individuals and 11.10% had someone living alone who was 65 years of age or older. The average household size was 2.46 and the average family size was 2.94.
