Massachusetts's 6th congressional district is located in northeastern Massachusetts. It contains most of Essex County, including the North Shore and Cape Ann, as well as part of Middlesex County. It is represented by Seth Moulton, who has represented the district since January 2015. The shape of the district went through minor changes effective from the elections of 2012 after Massachusetts congressional redistricting to reflect the 2010 census. The towns of Tewksbury and Billerica were added, along with a small portion of the town of Andover.

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.