Belfast Duncairn was a constituency of the Parliament of Northern Ireland.

Belfast Duncairn was a borough constituency comprising part of northern Belfast.

It was created in 1929 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.

It was always won by Unionist candidates, although labour movement and independent unionist candidates often contested it.