The Irish Free State (Saorstát Éireann) (1922-1937) was the state established as a Dominion on 6 December 1922 under the Anglo-Irish Treaty, signed by the British government and Irish representatives exactly twelve months beforehand.

On the day the Irish Free State was established, it comprised the entire island of Ireland but Northern Ireland almost immediately exercised its right under the Treaty to opt out of the new state. The Irish Free State replaced Southern Ireland (itself established on 3 May 1921 by the British Government under the Government of Ireland Act 1920), a de jure autonomous region of the United Kingdom of Great Britain and Ireland. The Irish Free State also effectively replaced the self-proclaimed but in many respects de facto Irish Republic (itself established on 21 January 1919). Similarly, the new government of the Irish Free State replaced both the Provisional Government of Southern Ireland and the Government of the Irish Republic although W. T. Cosgrave, the first President of the Executive Council of the Irish Free State had, in any event, led both governments since August 1922.