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.