Irish Boundary Commission

The Irish Boundary Commission (Irish: Coimisiún na Teorainne) was a commission which met in 1924–25 to decide on the precise delineation of the border between the Irish Free State and Northern Ireland. The 1921 Anglo-Irish Treaty, which ended the Anglo-Irish War, provided for such a commission if Northern Ireland chose to secede from the Irish Free State, an event that occurred as expected two days after the Free State's inception on 6 December 1922. The governments of the United Kingdom, of the Irish Free State and of Northern Ireland were to nominate one member each to the commission. When the Northern government refused to cooperate, the British government assigned a Belfast newspaper editor to represent Northern Irish interests.

The provisional border in 1922 was that which the Government of Ireland Act 1920 made between Northern Ireland and Southern Ireland. Irish nationalists hoped for a considerable transfer of land to the Free State, on the basis that most border areas had nationalist majorities. However, the Commission recommended relatively small transfers, and in both directions. This was leaked to the Morning Post in 1925, causing protests from both unionists and nationalists. In order to avoid the possibility of further disputes, the British, Free State, and Northern governments agreed to suppress the overall report, and the existing border was ratified by W. T. Cosgrave, Sir James Craig, and Stanley Baldwin on 3 December 1925 as part of a wider agreement including a resolution of outstanding financial matters. The commission's report was eventually published in 1969.