North Down was a constituency of the Parliament of Northern Ireland.
It was created when the House of Commons (Method of Voting and Redistribution of Seats) Act (Northern Ireland) 1929 introduced first-past-the-post elections throughout Northern Ireland.
The constituency survived unchanged until 1969, when it gained part of Mid Down, but the eastern half of the seat was split away to form Bangor.
The original seat was centred on the town of Bangor and urban district of Holywood, and it also included parts of the rural districts of Castlereagh and Newtownards.
It was sometimes contested by Northern Ireland Labour Party, Ulster Liberal Party and independent Unionist candidates, with only the independent Unionist receiving more than one third of the votes cast.