Fairfield is a city in Butler and Hamilton counties in the U.S. state of Ohio, and a residential suburb of nearby Cincinnati. Fairfield was incorporated in 1955. The population was 42,510 at the 2010 census. It includes the former hamlet of Symmes Corner, named after Celadon Symmes. The city school district is one of the largest in Ohio, with Fairfield High School graduating 842 students in June 2009.