Massachusetts's 3rd congressional district is located in northeastern and central Massachusetts.
Massachusetts congressional redistricting after the 2010 census has greatly changed the borders of this congressional district, largely dividing it between the new 2nd and 4th districts, with the new 3rd district covering only a few towns from the old district. Effective with the elections of 2012, Worcester is in the new 2nd district and the new 3rd district is similar to the old 5th district, largely covering the Merrimack valley including Lowell, Lawrence and Haverhill.
The district is represented by Democrat Niki Tsongas.
In Essex County: Precincts 2 through 7 and Precinct 9 in Andover, Haverhill, Lawrence, and Methuen.
In Middlesex County: Acton, Ashby, Ayer, Boxborough, Carlisle, Chelmsford, Concord, Dracut, Dunstable, Groton, Hudson, Littleton, Lowell, Marlborough, Maynard, Pepperell, Shirley, Stow, Townsend, Tyngsborough, Westford, and Precinct 1 in Sudbury.
In Worcester County: Ashburnham, Berlin, Bolton, Clinton, Fitchburg, Gardner, Harvard, Lancaster, Lunenburg, Westminster, and Precincts 1A, 2 and 3 in Winchendon.
In Bristol County: Attleboro, Fall River (Wards 1-3; Ward 4, Precincts A and B; Ward 5, Precincts A and B; Ward 6, Precincts B and C; and Ward 8, Precinct D), North Attleborough, Rehoboth, Seekonk, Somerset, Swansea.
In Middlesex County: Ashland, Holliston, Hopkinton, Marlborough.
In Norfolk County: Franklin, Medway, Plainville, Wrentham.
In Worcester County: Auburn, Boylston, Clinton, Holden, Northborough, Paxton, Princeton, Rutland, Shrewsbury, Southborough, West Boylston, Westborough, Worcester.