Hadley is a town in Hampshire County, Massachusetts, United States. The population was 5,325 at the 2020 census. It is part of the Springfield, Massachusetts Metropolitan Statistical Area. The area around the Hampshire and Mountain Farms Malls along Route 9 is a major shopping destination for the surrounding communities.

Hampshire County is a historical and judicial county located in the U.S. state of Massachusetts. As of the 2020 census, the population was 162,308. Its most populous municipality is Amherst, its largest town in terms of landmass is Belchertown, and its traditional county seat is Northampton. The county is named after the county Hampshire, in England. Hampshire County is part of the Springfield, MA Metropolitan Statistical Area. Together with Hampden County, Hampshire County municipalities belong to the Pioneer Valley Planning Commission.