Derby is an unincorporated community along the Ohio River in far southern Union Township, Perry County, Indiana, United States. It lies at the intersection of State Roads 66 and 70 above the city of Tell City, the county seat of Perry County. Its elevation is 449 feet (137 m), and it is located at (38°1′49″N86°31′38″W) (38.0303400, -86.5272018).