Fayette County is a county located in the U.S. state of Ohio. As of the 2020 census, the population was 28,951. Its county seat and largest city is Washington Court House. The county was named for the Marquis de Lafayette, a Frenchman who was an officer in the American Army in the Revolution, when established on March 1, 1810.

Washington Court House is a city in Union Township, Fayette County, Ohio. It is the county seat of Fayette County and is located between Cincinnati and Columbus. The population grew almost 1.5% from 2010 to 2020 approaching 14,401 people according to the 2020 census results. The area was initially settled by Virginia veterans of the American Revolution, who received the land from the government as payment for their service in the war.