The Republic of Ireland Act was an enactment of Oireachtas Éireann passed in 1948, which came into force on April 18, 1949 and which declared that the official description of Éire was to be the Republic of Ireland.

The Act

Between 1922 and 1937, the 26 county Irish state was technically a British dominion known as the Irish Free State. In 1937, a new constitution was introduced which renamed the twenty-six county state ' Éire, or in the English language, Ireland '. (Article 4 of the constitution, Bunreacht na hÉireann. The name 'Éire' is given constitutional superiority.) The official description of the state is Republic of Ireland, according to The Republic of Ireland Act, 1948, which came into effect on Easter Monday, April 18, 1949. A change of name would have necessitated a constitutional amendment and referendum. The Act itself is quite short, running to just 5 brief sections and is therefore easy to quote in full.

Number 22 of 1948

The Republic of Ireland Act, 1948

An act to repeal the Executive Authority (external relations) Act 1936, to declare that the description of the state shall be the Republic of Ireland, and to enable the President to exercise the executive power of any executive function of the state in or in connection with its external relations. (21st December, 1948)

Be it enacted by the Oireachtas as follows:-

1. The Executive Authority (External Relations) Act 1936 (No.58 of 1936) is hereby repealed.
2. It is hereby declared that the description of the State shall be the Republic of Ireland.
3. The President, on the authority and on the advice of the Government, may exercise the executive power or any executive function of the State in or in connection with its external relations.
4. This Act shall come into operation on such day as the Government may by order appoint.
5. This Act may be cited as The Republic of Ireland Act, 1948.

This ended the difficult period of transition from British rule to the Republic. The Civil War had been fought in 1922–23 on the issue of whether independence without immediately becoming a Republic was acceptable.

The Name of the State

Though technically only a description, the term Republic of Ireland is now treated in most instances as the Irish state's official name. However, for some governmental, legal, and diplomatic purposes the official name "Ireland" is sometimes used. For example treaties are signed on behalf of the Government of 'Ireland', while Republic of Ireland is generally referred to as 'Ireland' in terms of its membership of the United Nations, European Union, etc. Many states accredit ambassadors to 'Ireland', some use 'Republic of Ireland' while some avoid naming the state at all, preferring to use the nomenclature of the President of Ireland, signing the letters to 'President Hillery' or 'President McAleese'. (While the Irish state has accepted credentials addressed to 'Ireland', the 'Republic of Ireland', or the name of the president, it will not accept credentials addressed to the 'Irish Republic'.)

The 'Irish Republic' is unacceptable as it is the name used in the declaration of independence in 1919, and encompassed all 32 counties. (Éamon de Valera was thus President of the Irish Republic 1919–1921 and President of Ireland 1959–73). Letters were exchanged between President Hillery and Queen Elizabeth II to avoid political embarrassment over the terms "Ireland" and "Northern Ireland" in the states' titles.

External Relations Act, 1936

The Act repealed the External Relations Act, 1936. Under that Act, King George VI as King of Ireland acted as the Irish head of state in international relations. He accredited ambassadors and on Ireland's behalf accepted credentials appointing foreign ambassadors to Ireland. The Republic of Ireland Act removed this role (the last remaining role) from the King and vested instead in the President of Ireland, making the then President of Ireland, Sean T. O'Kelly unambiguously the Irish head of state.

The Republic

The Republic of Ireland Act amounted to a final declaration of an Irish republic. Irish membership of the Commonwealth of Nations automatically lapsed and neccessitated the introduction of the Ireland Act 1949 by Westminster. The then government, under John A. Costello opted not to reapply for membership, a decision criticised by then Leader of the Opposition Eamon de Valera, who considered applying for membership in the 1950s. (De Valera's grandson, Eamon O'Cuiv, now an Irish government minister, in the 1990s again advocated Irish membership of the Commonwealth.)

In the 1990s the All Party Oireachtas Committee on the Constitution considered amending Bunreacht na hÉireann to mention that Ireland is a republic. It decided against, eventually. This was the second time that such an amendment was considered by committee.