Mary Lou McDonald

Irish politician who has served as Leader of the Opposition in Ireland since June 2020 and President of Sinn Féin since February 2018. She has been a Teachta Dála (TD) for the Dublin Central constituency since 2011. She previously served as vice president of Sinn Féin from 2009 to 2018 and a Member of the European Parliament (MEP) for the Dublin constituency from 2004 to 2009.

On 10 February 2018, McDonald succeeded longtime party leader Gerry Adams as president of Sinn Féin, following a special ardfheis (party conference) in Dublin. In the 2020 general election, Sinn Féin's performance improved significantly and it was the first time in almost a century that neither Fianna Fáil nor Fine Gael won the most votes. Sinn Féin achieved the second-highest number of seats at 37, one behind Fianna Fáil's 38 seats.

Following Micheál Martin's appointment as Taoiseach in June 2020, after the formation of a Fianna Fáil, Green Party and Fine Gael coalition, McDonald became Leader of the Opposition. She is the first woman to occupy that position and the first to come from a party other than Fianna Fáil or Fine Gael since the Labour Party's Thomas Johnson in 1927.

McDonald has asthma. In April 2020, she announced that she had tested positive for COVID-19 following a test she took on 28 March. In a statement she said that she had recovered from the condition but had developed pleurisy in her right lung. She said that the Public Health Doctor had told her that she was no longer infected or infectious. In 2023, McDonald confirmed she had undergone a hysterectomy, to remove her ovaries and womb. Her recovery went well and she soon returned to her political work.

McDonald's husband, Martin Lanigan, works as a gas control superintendent for the emergency dispatch division of Gas Networks Ireland, a state infrastructure provider. They have two children. She lives in Cabra, Dublin.