Fairfield is an unincorporated community in northeastern Billings County, North Dakota, United States. It lies along U.S. Route 85 northwest of the city of Medora, the county seat of Billings County. Its elevation is 2,756 feet (840 m). Although it is unincorporated, it has a post office, with the ZIP code of 58627. Fairfield is part of the Dickinson Micropolitan Statistical Area.