MacBride is born in Paris on January 26, 1904. He is the son of Major John MacBride and Maud Gonne. After his father’s execution for his participation in the Easter Rising of 1916, MacBride is sent to school at Mount St. Benedict’s, Gorey, County Wexford in Ireland. In 1919, at the age of 15, he joins the Irish Volunteers, which fights as part of the Irish Republican Army, and takes part in the Irish War of Independence. He is imprisoned by the Irish Free State but is released in 1924 and resumes his IRA activities. He returns to Dublin in 1927 and becomes the Director of Intelligence of the IRA.
Toward the end of the 1920s, after many supporters have left the IRA to join Fianna Fáil, some members start pushing for a more left-wing agenda. After the IRA Army Council votes down the idea, MacBride launches a new movement, Saor Éire (“Free Ireland”), in 1931. Although it is a non-military organisation, Saor Éire is declared unlawful along with the IRA, Cumann na mBan, and nine other organizations.
In 1936, MacBride becomes Chief of Staff of the IRA after Moss Twomey is sent to prison for three years. At the time, the movement is in a state of disarray, with conflicts between several factions and personalities. In 1937, he is called to the bar and then resigns from the IRA when the Constitution of Ireland is enacted later that year. As a barrister, he frequently defends IRA political prisoners, but is not unsuccessful in stopping the execution of Charlie Kerins in 1944 who is convicted of killing Garda Detective Dennis O’Brien in 1942. In 1946, during the inquest into the death of Seán McCaughey, he embarrasses the authorities by forcing them to admit that the conditions in Portlaoise Prison are inhumane.
In 1946, MacBride founds the republican/socialist party Clann na Poblachta, hoping it would replace Fianna Fáil as Ireland’s major political party. In October 1947, he wins a seat in Dáil Éireann at a by-election in the Dublin County constituency. However, at the 1948 Irish general election Clann na Poblachta wins only ten seats.
MacBride is serving as Minister of External Affairs when the Council of Europe drafts the European Convention on Human Rights. He serves as President of the Committee of Ministers of the Council of Europe from 1949 to 1950 and is credited with being a key force in securing the acceptance of this convention, which is finally signed in Rome on November 4, 1950. He is instrumental in the implementation of the repeal of the External Relations Act and the passing of the Republic of Ireland Act 1948 which comes into force in 1949.
Clann na Poblachta is reduced to only two seats after the 1951 Irish general election. MacBride keeps his seat and is re-elected again at the 1954 Irish general election. Opposing the internment of IRA suspects during the Border Campaign (1956–62), he contests both the 1957 and 1961 Irish general elections but fails to be elected both times. He then retires from politics but continues practicing as a barrister. He expresses interest in running as an independent candidate in the 1983 Irish presidential election, but does not receive sufficient backing and ultimately does not enter the contest.
Throughout the 1950s, 1960s, and 1970s, MacBride works tirelessly for human rights worldwide. He is a founding member of Amnesty International and serves as its International chairman from 1961 until 1975. During the 1980s, he initiates the Appeal by Lawyers against Nuclear War which is jointly sponsored by the International Peace Bureau and the International Progress Organization.
MacBride is awarded the Nobel Peace Prize in 1974 as a man who “mobilised the conscience of the world in the fight against injustice.” He later receives the Lenin Peace Prize (1975–76) and the UNESCO Silver Medal for Service (1980).
In his later years, MacBride lives in his mother’s home, Roebuck House, that served as a meeting place for many years for Irish nationalists, as well as in the Parisian arrondissement where he grew up with his mother, and enjoyed strolling along boyhood paths. In 1978, he receives the Golden Plate Award of the American Academy of Achievement.
MacBride dies in Dublin on January 15, 1988, just eleven days shy of his 84th birthday. He is buried in a simple grave in Glasnevin Cemetery, Dublin, with his mother, and wife who died in 1976.