Amesbury is a city in Essex County, Massachusetts, United States, located on the left bank of the Merrimack River near its mouth, upstream from Salisbury and across the river from Newburyport and West Newbury. The population was 17,366 at the 2020 United States Census. A former farming and mill town, Amesbury is today largely residential. It is one of the two northernmost towns in Massachusetts.

Essex County is a county in the northeastern part of the U.S. state of Massachusetts. At the 2020 census, the total population was 809,829, making it the third-most populous county in the state, and the seventy-eighth-most populous in the country. It is part of the Greater Boston area. The largest city in Essex County is Lynn. The county was named after the English county of Essex. It has two traditional county seats: Salem and Lawrence. Prior to the dissolution of the county government in 1999, Salem had jurisdiction over the Southern Essex District, and Lawrence had jurisdiction over the Northern Essex District, but currently these cities do not function as seats of government. However, the county and the districts remain as administrative regions recognized by various governmental agencies, which gathered vital statistics or disposed of judicial case loads under these geographic subdivisions, and are required to keep the records based on them. The county has been designated the Essex National Heritage Area by the National Park Service.