Born in Northern Ireland, Onora O’Neill was educated in both the UK and Germany before going on to study philosophy, psychology and physiology at Oxford University. Her doctorate was completed at Harvard University, after which she taught at Barnard College, the women's college at Columbia University, New York.

In 1977 she returned to the UK to work at the University of Essex where she became Professor of Philosophy before leaving in 1992 to take on the post of Principal of Newnham College, Cambridge University.

She has chaired the Nuffield Council on Bioethics and the Human Genetics Advisory Commission, and she is currently chair of the Nuffield Foundation. She has been President of the Aristotelian Society, and a member of the Animal Procedures (Scientific) Committee. In 1999 she was made a life peer as Baroness O'Neill of Bengarve, and sits as a crossbencher.

She has written widely on political philosophy and ethics, international justice, bioethics and the philosophy of Immanuel Kant. In 2002 she addressed the issue of trust in the BBC’s Reith Lectures.  In an exclusive article for Open2, she explains her view of trust.