West 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.
It survived unchanged, returning one Member of Parliament, until the Parliament of Northern Ireland was temporarily suspended in 1972, and then formally abolished in 1973.
The seat included the town of Banbridge, and also certain district electoral divisions of the rural districts of Banbridge and Newry No.1.
It was contested on three occasions by independent unionists, each of whom won over 40% of the votes cast, and once by a communist candidate.