Mary Ellen O’Connell is Research Professor of International Dispute Resolution at the Kroc Institute. She also is the Robert and Marion Short Professor of Law at Notre Dame, a position which she has held since 2005.

O’Connell's research focuses on international legal theory and international law on the use of force. She is the author or editor of numerous books and articles, including What is War? An Investigation in the Wake of 9/11 (Martinus Nijhoff, 2012); International Dispute Resolution, Cases and Materials (Carolina, 2012); The Power and Purpose of International Law, Insights from the Theory and Practice of Enforcement (Oxford, 2011); The International Legal System: Cases and Materials (Foundation 2010); International Law on the Use of Force: Cases and Materials (Foundation, 2009); The Power and Purpose of International Law: Insights from the Theory and Practice of Enforcement (OUP 2008); International Law and the “Global War on Terrorism”: Lectures for the University of Paris II (Assas-Pantheon, 2007); Redefining Sovereignty, The Use of Force After the Cold War (Transnational, 2005); International Dispute Settlement, Library of Essays in International Law (Ashgate/Dartmouth, 2003); Proceedings of the 2002 Annual Meeting of the American Society of International Law (ASIL); Politics, Values and Functions: International Law in the 21st Century: Essays in Honor of Prof. Louis Henkin (Kluwer Law International, 1997); and International Law and the Use of Force (Little, Brown & Co., 1993). 

O'Connell teaches a graduate-level course on international dispute resolution, advises Kroc graduate students, collaborates with Kroc faculty on research, and contributes to policy studies and public outreach. As an engaged Catholic intellectual, she deepens Kroc’s expertise in Catholic social ethics and theory of justice.

She chaired the Use of Force Committee of the International Law Association from 2005 to 2010 and is currently a vice-president of the American Society of International Law. From 1995-1998, Professor O’Connell was a professional military educator for the Department of Defense in Garmisch-Partenkirchen, Germany.

Prior to joining the Notre Dame faculty, O'Connell was the William B. Saxbe Designated Professor of Law at Ohio State University. She earned her J.D. from Columbia University, and she has taught at Indiana University School of Law; the Bologna Center of The Johns Hopkins University, Paul H. Nitze School of Advanced International Studies, Bologna, Italy; the George C. Marshall European Center for Security Studies; and the University of Cincinnati College of Law.