Greene County is located in the southwestern portion of Ohio. As of the 2020 census, the population was 167,966. Its county seat is Xenia and its largest city is Beavercreek. The county was established on March 24, 1803 and named for General Nathanael Greene, an officer in the Revolutionary War. Greene County is part of the Dayton, OH Metropolitan Statistical Area.

Ohio's 10th congressional district is represented by Representative Mike Turner (R). The district is based in southwestern Ohio and consists of Montgomery County, Greene County, and a portion of Clark County.