Fayette County is a county located in the U.S. state of Ohio. As of the 2010 census, the population was 29,030. Its county seat 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.Fayette County comprises the Washington Court House, OH Micropolitan Statistical Area, which is also included in the Columbus-Marion-Zanesville, OH Combined Statistical Area.