The leader of the opposition () in Ireland is a term sometimes used to describe the politician who leads the largest party in the parliamentary opposition in Dáil Éireann, the house of representatives of the Oireachtas (the Irish parliament). In the Dáil, the leader of the opposition sits on the right-hand side of the Ceann Comhairle and directly opposite the Taoiseach. The role is not an official one and is not recognised in the Irish constitution, nor in legislation.
The leader of the opposition is, by convention, the leader of the largest political party in the Dáil that is not in government. Opposition leaders leading a political party with five members or more have full speaking rights under Dáil standing orders; smaller parties and independent politicians are allowed to speak less often.
Historically the two largest parties have nearly always been Fianna Fáil and Fine Gael, and so the position of leader of the opposition has alternated between them. However, immediately following Irish independence from the UK in 1922, the leader of the Labour Party acted as leader of the opposition as Sinn Féin, and later Fianna Fáil, refused to take their seats in Dáil Éireann. After the 2011 general election Fine Gael became the largest party in Dáil Éireann and the Labour Party for the first time became the second largest. However, since Labour and Fine Gael entered a coalition government, the third largest party, Fianna Fáil, led the opposition in the 31st Dáil.
To date there have been 18 Opposition Leaders, 10 of whom have served terms as Taoiseach. The leader of the opposition is Mary Lou McDonald of Sinn Féin, following the formation of a government of Fianna Fáil, Fine Gael and the Green Party on 27 June 2020. She is the first female Irish opposition leader and the second to come from a party other than Fianna Fáil or Fine Gael, following Labour Party's Thomas Johnson in 1927.
Leaders of the opposition
- Leaders who later became Taoiseach are indicated in bold.
{| class="wikitable"
|-
!rowspan=2|Name<br />
!rowspan=2|Portrait
!rowspan=2|Constituency
!colspan=2|Term of office
!rowspan=2 colspan=2|Party
!rowspan=2 colspan=2|Taoiseach
|-
!From!!To
|-
|align=center|Éamon de Valera<br />
|60px
|Clare
|9 January 1922
! style="background-color: " |
|Sinn Féin (Anti-Treaty)
! style="background-color: " |
|Arthur Griffith<br/>(1922)
|-
|align=center|Thomas Johnson<br />
|60px
|Dublin County
|9 September 1922
|11 August 1927
! style="background-color: " |
|Labour Party
! style="background-color: " rowspan=2|
|rowspan=2|W. T. Cosgrave<br/>(1922–1932)
|-
|align=center|Éamon de Valera<br />
! style="background-color: " |
|Fianna Fáil
|-
|rowspan=2 align=center|W. T. Cosgrave<br />
|rowspan=2|60px
|rowspan=2|Cork Borough
|rowspan=2|9 March 1932
|rowspan=2|January 1944
! style="background-color: " |
|Cumann na nGaedheal
! style="background-color: " rowspan=4|
|rowspan=4|Éamon de Valera<br/>(1932–1948)
|-
! style="background-color: " rowspan=3|
|rowspan=3|Fine Gael
|-
|align=center|Thomas F. O'Higgins<br />
|60px
|Tipperary
|9 June 1944
|18 February 1948
|-
|align=center|Éamon de Valera<br />
! style="background-color: " |
|Fianna Fáil
! style="background-color: " |
|John A. Costello<br/>(1948–1951)
|-
|align=center|John A. Costello<br />
|-
|align=center|Éamon de Valera<br />
! style="background-color: " |
|Fianna Fáil
! style="background-color: " |
|John A. Costello<br/>(1954–1957)
|-
|rowspan=3|Seán Lemass<br/>(1959–1966)
|rowspan=2|60px
|rowspan=2|Dún Laoghaire and Rathdown
|rowspan=2|21 April 1965
|-
|Jack Lynch<br/>(1966–1973)
|-
|align=center|Jack Lynch<br />
|rowspan=2|60px
|rowspan=2|Dublin South-East
|rowspan=2|5 July 1977
|rowspan=2|30 June 1981
! style="background-color: " rowspan=2|
|rowspan=2|Fine Gael
! style="background-color: " rowspan=2|
|Jack Lynch<br/>(1977–1979)
|-
|align=center|Garret FitzGerald<br />
|-
|align=center|Charles Haughey<br />
! style="background-color: " |
|Fianna Fáil
! style="background-color: " |
|Garret FitzGerald<br/>(1982–1987)
|-
|align=center|Bertie Ahern<br />
! style="background-color: " |
|Fianna Fáil
! style="background-color: " |
|John Bruton<br/>(1994–1997)
|60px
|Meath
|26 June 1997
! style="background-color: " rowspan=4|
|rowspan=4|Fine Gael
! style="background-color: " rowspan=4|
|rowspan=3|Bertie Ahern<br/>(1997–2008)
|60px
|Limerick East
|9 February 2001
|rowspan=2|60px
|rowspan=2|Mayo
|rowspan=2|6 June 2002
|rowspan=2|9 March 2011
|-
|Brian Cowen<br/>(2008–2011)
|-
|rowspan=2 align=center|Micheál Martin<br />
|rowspan=2|60px
|rowspan=2|Cork South-Central
|rowspan=2|9 March 2011
!rowspan=2 style="background-color: " |
|rowspan=2|Fianna Fáil
! style="background-color: " |
|Enda Kenny<br/>(2011–2017)
|-
|rowspan=4 align=center|Mary Lou McDonald<br />
|rowspan=4|60px
|rowspan=4|Dublin Central
|rowspan=4|27 June 2020
|rowspan=4|Incumbent
!rowspan=4 style="background-color: " |
|rowspan=4|Sinn Féin
! style="background-color: " |
|Micheál Martin<br/>(2020–2022)
|-
! style="background-color: " |
|Simon Harris<br/>(2024–2025)
|-
! style="background-color: " |
|Micheál Martin<br/>(2025–present)
|60px
|Kildare
|13 June 1951
|2 June 1954
! style="background-color: " |
|Labour Party
! style="background-color: " |
|John A. Costello<br/>(1951–1954)
|-
|align=center|Seán MacBride<br />
|60px
|Dublin South-West
|2 June 1954
|20 March 1957
! style="background-color: " |
|Clann na Poblachta
! style="background-color: " |
|Éamon de Valera<br/>(1954–1957)