The functions and powers of the President, Dáil and Seanad derive from the Constitution of Ireland and law. Under the Constitution, the President of Ireland (Uachtarán na hÉireann) is elected by the direct vote of the people. Every citizen of thirty-five years of age or over is eligible for the office. Every citizen who has a right to vote at an election for members of Dáil Éireann has the right to vote at an election for President. The President's term of office is seven years. A President can be re-elected once only. Presidents elected since the creation of the office in 1937 have been Dr. Douglas Hyde (1938-1945), Seán T. Ó Ceallaigh (1945-1959), Éamon de Valera (1959-1973), Erskine Childers (1973-1974), Cearbhall Ó Dálaigh (1974-1976), Dr. Patrick Hillery (1976-1990), Mary Robinson (1990-1997). President Mary McAleese was inaugurated on 11 November, 1997 for a seven year term of office.

The President is Head of State only and does not have executive functions. The Constitution, however, envisages the President as more than a ceremonial Head of State. It gives the President certain powers that make the President in effect the guardian of the Constitution. The President normally acts on the advice and authority of the Government.

On the nomination of Dáil Éireann the resident appoints the Taoiseach (Prime Minister). On the advice of the Taoiseach and with the prior approval of Dáil Éireann the President appoints members of the Government. On the advice of the Taoiseach, the President accepts the resignation or terminates the appointment of a member of the Government. Dáil Éireann is summoned and dissolved by the President on the advice of the Taoiseach. Before a Bill may become law, it must have the President's signature.

The President has certain discretionary powers. First, the President may, after consultation with the Council of State, an advisory body to the President, refer any Bill to the Supreme Court for a decision as to whether it contains anything repugnant to the Constitution. Secondly, if a majority of the Seanad and not less than one-third of the Dáil petition the President to decline to sign a Bill on the grounds that it contains a proposal of such national importance that the will of the people thereon ought to be ascertained, the President may accede to the request after consultation with the Council of State. In these circumstances the President may sign the Bill only when the proposal has been approved by the people in a referendum or by a new Dáil after a dissolution and a General Election. The President has one power which may be exercised at his or her absolute discretion. This allows the President to refuse to dissolve the Dáil on the advice of a Taoiseach who has ceased to retain the support of a majority in the Dáil. The supreme command of the defence forces is vested in the President.

There is no Vice-President of Ireland. If the President dies in office, or is incapacitated, or is abroad, or is removed from office or fails to carry out functions enjoined on the office by the Constitution, the Constitution provides for a Commission to act in his or her place. The Commission would consist of the Chief Justice, the Chairman of Dáil Éireann, and the Chairman of Seanad Éireann.