Dedham is a town in, and the county seat of, Norfolk County, Massachusetts, United States. Located on Boston's southwestern border, the population was 25,364 at the 2020 census. First settled by English colonists in 1635 and incorporated in 1636, Dedham established the first public school in America in 1643. Dedham is home to the Fairbanks House, the oldest surviving timber-frame house in the United States.