Fairfield County is part of the Columbus, OH Metropolitan Statistical Area.

[6] Fairfield County sits just on the edge of Ohio's Appalachian region.

While the once-glaciated northern portion of the county is fairly flat, as one travels south along U.S. 33 one can easily recognize the foothills of a mountainous region beginning around the village of Carroll.

Although not officially part of the state or federal definition of Appalachia, certain areas of Fairfield County—particularly those south of U.S. 22—bear a distinctly Appalachian feel in both physical geography and demographics.

A large portion of Buckeye Lake is located in northeastern Fairfield County.

Mudhouse Mansion, an allegedly haunted house, was located in the county.

21.90% of all households were made up of individuals, and 8.40% had someone living alone who was 65 years of age or older.

As of the 2010 United States Census, there were 146,156 people, 54,310 households, and 39,846 families living in the county.

[15] Prior to 1944, Fairfield County was Democratic in presidential elections, only voting for Republicans twice from 1856 to 1940.