Lynch is born on August 15, 1917, in Blackpool, on the north side of Cork, County Cork. He is educated at St. Vincent’s Convent on Peacock Lane, and later at the North Monastery Christian Brothers School. He sits his Leaving Certificate in 1936, after which he moves to Dublin and works with the Dublin District Milk Board, before returning to Cork to take up a position in the Circuit Court Office.
Lynch eventually decides on a legal career, is called to the bar (1945), resigns from the civil service, and practices on the Cork circuit. He already enjoys a national reputation as a sports hero having won five All-Ireland medals as a Cork hurler and another as a footballer. He joins Fianna Fáil and wins a seat in Dáil Éireann, the lower house of the Oireachtas, in 1948. He works closely with Éamon de Valera in opposition (1948–51), and de Valera appoints him a parliamentary secretary in 1951–54, minister for the Gaeltacht in 1957, and Minister for Education in 1957–59. When Seán Lemass succeeds de Valera as Taoiseach in 1959, he makes Lynch Minister for Industry and Commerce and in 1965–66 Minister for Finance.
Lemass’s retirement in 1966 causes an internal party conflict over the succession that leads to Lynch’s selection as a compromise candidate, a position he reluctantly accepts. In November of that year he becomes leader of Fianna Fáil and Taoiseach. In June 1969 he becomes the only Fianna Fáil leader other than de Valera to win an overall majority in a general election. In 1969–1973 Lynch plays an important role when civil unrest leads to the collapse of the government of Northern Ireland and poses a threat to the stability of the Irish state. He fires two cabinet ministers who are suspected of involvement in smuggling arms to the Provisional Irish Republican Army (IRA). He also creates a consensus in Irish party politics on a policy of conciliation and cooperation with the British government in seeking a solution to the Northern Ireland problem based on establishing power-sharing between the unionist majority and the Roman Catholic minority.
In 1972 Lynch wins an 83 percent majority in a referendum on Ireland’s entry into the European Economic Community. On January 1, 1973, Ireland becomes a member. Although he is defeated in the 1973 elections, he again demonstrates his remarkable popularity at the polls in 1977 when Fianna Fáil wins their largest and their last overall majority. In December 1979, however, discouraged by challenges to his authority from party colleagues, he resigns his leadership and soon after retires from politics. He serves on a number of corporate boards after his retirement.
In 1992 Lynch suffers a severe health setback, and in 1993 suffers a stroke in which he nearly loses his sight. Following this he withdraws from public life, preferring to remain at his home with his wife Máirín where he continues to be dogged by ill-health.
Lynch dies in the Royal Hospital, Donnybrook, Dublin on October 20, 1999 at the age of 82. He is honoured with a state funeral which is attended by the President of Ireland Mary McAleese, Taoiseach Bertie Ahern, former Taoisigh John Bruton, Albert Reynolds and Charles Haughey, and various political persons from all parties. The coffin is then flown from Dublin to Cork where a procession through the streets of the city draw some of the biggest crowds in the city’s history. After the Requiem Mass celebrated in his home parish of the Cathedral of St. Mary and St. Anne, Lynch’s friend and political ally, Desmond O’Malley, delivers the graveside oration, paying tribute to Lynch’s sense of decency. He is buried in St. Finbarr’s Cemetery in Cork.