Southern Ireland ( ) was a short-lived autonomous region of the United Kingdom established on 3 May 1921 and dissolved on 6 December 1922.
Southern Ireland was established under the Government of Ireland Act 1920 together with its sister region, Northern Ireland. It was envisaged that Southern Ireland would have the following institutions:
* a Parliament of Southern Ireland, consisting of the King, the Senate of Southern Ireland, and the House of Commons of Southern Ireland;
* a Government of Southern Ireland;
* the Supreme Court of Judicature of Southern Ireland;
* the Court of Appeal in Southern Ireland; and
* His Majesty's High Court of Justice in Southern Ireland.
It was also envisaged that Southern Ireland would share the following institutions with Northern Ireland:
* the Lord Lieutenant of Ireland;
* a Council of Ireland; and
* a High Court of Appeal for Ireland.
The Parliament, although legally established, never functioned (for example, it never passed an Act). The House of Commons of Southern Ireland met just once with only four members present. No Government of Southern Ireland was ever established either. The Council of Ireland was to be established "[w]ith a view to the eventual establishment of a Parliament for the whole of Ireland", but it never came into being. The notable exception to the failure of the institutions of Southern Ireland was its courts, all of which functioned.