The Tánaiste (plural: Tánaistí), or, more formally, An Tánaiste, is the deputy prime minister of Ireland. The Taoiseach (prime minister) nominates a member of the govern-ment to the position of Tánaiste. The current Tánaiste is Mary Coughlan, TD. Tánaiste was originally the Irish word for the heir of the chief (taoiseach) or king (rí), under the Gaelic system of tanistry. Before independence, the British Viceroy was sometimes referred to in the Irish language as An Tánaiste-Rí, literally 'the deputy king'.

Overview:

The office was created in the 1937 Constitution of Ireland, replacing the previous office of Vice-President of the Executive Council that had existed under the Free State constitution. The Tánaiste acts in the place of the Taoiseach during his or her temporary absence, and, until a successor has been appointed, in the event of the Taoiseach's death or permanent incapacitation. The Tánaiste must be a member of Dáil Éireann, and is ex-officio a member of the Council of State. The Tánaiste would usually chair meetings of the government if the Taoiseach is absent or take questions on his behalf in the Dáil or Seanad.

Aside from these duties, the title is largely honorific in practice. The constitution does not give the Tánaiste specific powers other than deputising for the Taoiseach. Under a coalition government the position is commonly held by the leader of the second-largest party who in this situation is free to head any department he or she wants. Recent Tánaistí, such as Michael McDowell, Mary Harney and Dick Spring, have been leaders of smaller parties. In a single-party government the Tánaiste is often an 'elder statesman' holding one of the less important ministerial portfolios.

List of office-holders:

Seán T. O'Kelly (29 December 1937 - 14 June 1945)
Seán Lemass (4 June 1945 - 18 February 1948)
William Norton (18 February 1948 - 13 June 1951)
Seán Lemass (13 June 1951 - 2 June 1954)
William Norton (2 June 1954 - 20 March 1957)
Seán Lemass (20 March 1957 - 23 June 1959)
Seán MacEntee (23 June 1959 - 21 April 1965)
Frank Aiken (21 April 1965 - 2 July 1969)
Erskine H. Childers (2 July 1969 - 14 March 1973)
Brendan Corish (14 March 1973 - 5 July 1977)
George Colley (5 July 1977 - 30 June 1981)
Michael O'Leary (30 June 1981 - 9 March 1982)
Ray MacSharry (9 March 1982 - 14 December 1982)
Dick Spring (14 December 1982 - 20 January 1987)
Peter Barry (20 January 1987 - 10 March 1987)
Brian Lenihan (10 March 1987 - 31 October 1990)
John Wilson (13 November 1990 - 12 January 1993)
Dick Spring(12 January 1993 - 17 November 1994)
Bertie Ahern (19 November 1994 - 15 December 1994)
Dick Spring (15 December 1994 - 26 June 1997)
Mary Harney (26 June 1997 - 13 September 2006)
Michael McDowell (13 September 2006 - 14 June 2007)
Brian Cowen (14 June 2007 - 7 May 2008)
Mary Coughlan (7 May 2008 - ?)