Pittsfield is the largest city and the county seat of Berkshire County, Massachusetts, United States. It is the principal city of the Pittsfield, Massachusetts Metropolitan Statistical Area which encompasses all of Berkshire County. Pittsfield’s population was 43,927 at the 2020 census. Although its population has declined in recent decades, Pittsfield remains the third-largest municipality in Western Massachusetts, behind only Springfield and Chicopee.

Berkshire County is the westernmost county in the U.S. state of Massachusetts. As of the 2020 census, the population was 129,026. Its largest city and traditional county seat is Pittsfield. The county was founded in 1761. The Berkshire Hills are centered on Berkshire County. Residents are known as Berkshirites. It exists today only as a historical geographic region, and has no county government, with the exception of the retirement board for former county workers, and certain offices such as the sheriff and registry of deeds.