<P> In accordance with the treaty , on 6 December 1922 the entire island of Ireland became a self - governing dominion called the Irish Free State ( Saorstát Éireann ) . Under the Constitution of the Irish Free State , the Parliament of Northern Ireland had the option to leave the Irish Free State one month later and return to the United Kingdom . During the intervening period , the powers of the Parliament of the Irish Free State and Executive Council of the Irish Free State did not extend to Northern Ireland . Northern Ireland exercised its right under the treaty to leave the new dominion and rejoined the United Kingdom on 8 December 1922 . It did so by making an address to the King requesting , `` that the powers of the Parliament and Government of the Irish Free State shall no longer extend to Northern Ireland . '' The Irish Free State was a constitutional monarchy sharing a monarch with the United Kingdom and other dominions of the British Commonwealth . The country had a governor - general ( representing the monarch ) , a bicameral parliament , a cabinet called the `` Executive Council '' , and a prime minister called the President of the Executive Council . </P>
<P> In accordance with the treaty , on 6 December 1922 the entire island of Ireland became a self - governing dominion called the Irish Free State ( Saorstát Éireann ) . Under the Constitution of the Irish Free State , the Parliament of Northern Ireland had the option to leave the Irish Free State one month later and return to the United Kingdom . During the intervening period , the powers of the Parliament of the Irish Free State and Executive Council of the Irish Free State did not extend to Northern Ireland . Northern Ireland exercised its right under the treaty to leave the new dominion and rejoined the United Kingdom on 8 December 1922 . It did so by making an address to the King requesting , `` that the powers of the Parliament and Government of the Irish Free State shall no longer extend to Northern Ireland . '' The Irish Free State was a constitutional monarchy sharing a monarch with the United Kingdom and other dominions of the British Commonwealth . The country had a governor - general ( representing the monarch ) , a bicameral parliament , a cabinet called the `` Executive Council '' , and a prime minister called the President of the Executive Council . </P>
when did the republic of ireland became independent
when did the republic of ireland became independent
6 December 1922
6 December 1922