Robinson was educated at Trinity College and King's Inns in Dublin and at Harvard University in the United States. She served at Trinity College (University of Dublin (Dublin, University of)) as Reid Professor of penal legislation, constitutional and criminal law, and the law of evidence (1969–75) and lecturer in European Community law (1975–90). In 1988 she established (with her husband) at Trinity College the Irish Centre for European Law. A distinguished constitutional lawyer and a renowned supporter of human rights, she was elected to the Royal Irish Academy and was a member of the International Commission of Jurists in Geneva (1987–90). She sat in the Seanad (upper chamber of Parliament) for the Trinity College constituency (1969–89) and served as whip for the Labour Party until resigning from the party over the Anglo-Irish Agreement of 1985, which she felt ignored unionist objections. She was also a member of the Dublin City Council (1979–83) and ran unsuccessfully in 1977 and 1981 for Dublin parliamentary constituencies.

Nominated by the Labour Party and supported by the Green Party and the Workers' Party, Robinson became Ireland's first woman president in 1990 by mobilizing a liberal constituency and merging it with a more conservative constituency opposed to the Fianna Fáil party. As president, Robinson adopted a much more prominent role than her predecessors, and she did much to communicate a more modern image of Ireland. Strongly committed to human rights, she was the first head of state to visit Somalia after it suffered from civil war and famine in 1992 and the first to visit Rwanda after the genocide in that country in 1994. Shortly before her term as president expired, she took up the post of UNHCHR. As high commissioner, Robinson changed the priorities of her office to emphasize the promotion of human rights at the national and regional levels; she was the first UNHCHR to visit China, and she also helped to improve the monitoring of human rights in Kosovo. In 2001 Robinson served as secretary-general of the World Conference against Racism, Racial Discrimination, Xenophobia and Related Intolerance, held in Durban, South Africa. (See also Sidebar: Children and Human Rights.) In 1998 she was elected chancellor of Trinity College.

After leaving her post at the UN, Robinson founded the nongovernmental organization Realizing Rights: The Ethical Globalization Initiative, in 2002. Its central concerns included equitable international trade, access to health care, migration, women's leadership, and corporate responsibility. She was also a founding member of the Council of Women World Leaders, served as honorary president of Oxfam International (a private organization that provides relief and development aid to impoverished or disaster-stricken communities worldwide), and was a member of the Club of Madrid (which promotes democracy). In 2004 Amnesty International awarded her its Ambassador of Conscience award for her human rights work.