Although born in Cork, Moynihan-Cronin is a native of Killarney, County Kerry. She is educated at St. Brigid’s Secondary School in Killarney, Dominican College Sion Hill in Dublin, and Skerry’s College, Cork. Her father, Michael Moynihan, is a TD for Kerry South from 1981 to 1987 and from 1989 to 1992. She works as a bank official before becoming involved in politics in 1991 when she is elected to Kerry County Council. She is first elected to Dáil Éireann at the 1992 Irish general election as a Labour Party TD for Kerry South, succeeding her father. She is re-elected at every election until 2007.
On October 11, 2005, Moynihan-Cronin announces that she will not stand for re-election at the forthcoming general election due to ill-health. Her decision to retire presents considerable difficulties for the Labour Party to retain her seat, as the party performed poorly at the 2004 Kerry County Council election, failing to elect any councillors within the county. However, on October 28, 2006, she announces that she will stand in the forthcoming general election, having overcome her health difficulties. However, she fails to retain her seat.
In June 2011, Moynihan-Cronin returns to politics when she is co-opted onto Kerry County Council to represent the Killarney area, filling the seat left vacant when Marie Moloney is elected to the 24th Seanad. In 2013, she stands down from the council and is replaced by Sean Counihan.
Zappone is nominated by Taoiseach Enda Kenny to the 24th Seanad in 2011, having been recommended by Eamon Gilmore, the then leader of Fine Gael‘s coalition partners, the Labour Party. With her Seanad nomination, she becomes the first openly lesbian member of the Oireachtas and the first member in a recognised same-sex relationship.
Zappone is elected to the Dáil for the Dublin South-West constituency at the 2016 Irish general election, becoming the first openly lesbian TD and, by her own reckoning, the world’s 32nd lesbian to be elected to a national parliament. In May 2016, after a delay in government formation, due to prolonged talks, she becomes Ireland’s first openly lesbian government Minister and the first Minister to have been openly gay at the time of appointment to cabinet, when Taoiseach Enda Kenny appoints her as the Minister for Children and Youth Affairs. She loses her seat at the February 2020 Irish general election and continues to serve as a minister until June 2020 on the election of a new government.
In July 2021, it is announced that Zappone is to be appointed to the newly created position of Special Envoy to the UN for Freedom of Opinion and Expression. It subsequently emerges that the proposed appointment had not been flagged in advance of the Cabinet meeting where it was proposed by Minister Simon Coveney, raising the concerns of the Taoiseach, Micheál Martin. However, he does not block the appointment, attracting criticism from within government, the opposition and the public, with Sinn Féin describing the appointment as “cronyism.”
In the following days it is reported that Zappone had lobbied for the creation of an appointment to the part-time position, which was not openly advertised or subject to a competition. Further controversy arises when it is reported that shortly prior to the announcement of her appointment, she had hosted a party for 50 guests, including politicians such as Leo Varadkar, at the Merrion Hotel, while the COVID-19 pandemic in the Republic of Ireland was ongoing. Comparisons are made between the party and the Oireachtas Golf Society scandal from earlier in the pandemic. On August 4, 2021, she announces that she will not take up the envoy role, saying “While I am honoured to have been appointed by the Government to be the Special Envoy on Freedom of Opinion and Expression, it is clear that criticism of the appointment process has impacted the legitimacy of the role itself. It is my conviction that a Special Envoy role can only be of real value to Ireland and to the global community if the appointment is acceptable to all parties.”
In September 2021, Zappone is invited to appear before the Oireachtas Committee on Foreign Affairs and Defence, but chooses not to attend. As a U.S. citizen and resident, the committee has no power to compel her attendance.