Belfast South was a borough constituency of the Parliament of Northern Ireland from 1921 to 1929.

It returned four MPs, using proportional representation by means of the single transferable vote.

[1] In May 1921, Dáil Éireann, the parliament of the self-declared Irish Republic run by Sinn Féin, passed a resolution declaring that elections to the House of Commons of Northern Ireland and the House of Commons of Southern Ireland would be used as the election for the Second Dáil.

Even following its abolition, Ballynafeigh, Cromac, and Windsor only ever elected Unionist MPs.

Woods declined the seat, having also been elected for Belfast West.