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.

Norfolk County is located in the U.S. state of Massachusetts. At the 2020 census, the population was 725,981. Its county seat is Dedham. It is the fourth most populous county in the United States whose county seat is neither a city nor a borough, and it is the second most populous county that has a county seat at a town. The county was named after the English county of the same name. Two towns, Cohasset and Brookline, are exclaves.