Peter Wallensteen, a leading international peace researcher, joined the Kroc Institute faculty in 2006. He spends the fall semesters in residence at Notre Dame, where he consults and collaborates with faculty on research projects, teaches a graduate seminar on international peace research, and lectures on peace research topics.

Wallensteen is a Senior Professor in the Department of Peace and Conflict Research at Sweden’s Uppsala University, where he directs the Uppsala Conflict Data Program as well as the Special Program on the Implementation of Targeted Sanctions. He previously was the first holder of the Dag Hammarskjöld Chair in Peace and Conflict Research (1985-2012).

He is the author of the widely used Understanding Conflict Resolution: Peace, War, and the Global System which was published in 2002 and in Arabic in 2006. The third edition was published in early 2012. In late 2011 he published Peace Research: Theory and Practice (Routledge 2011) which includes 13 previously published articles and five new essays. In 2010, Wallensteen and Isak Svensson published The Go-Between: Jan Eliasson and the Styles of Mediation (United States Institute of Peace), an analysis of one mediator's work in six crises. 

Wallensteen's interest in targeted sanctions led him to publish the edited volume International Sanctions: Between Wars and Words in 2005 (with Carina Staibano and with contributions by Kroc Institute sanctionsresearchers.) The report Making Targeted Sanctions Effective was the outcome of a large international process for improving sanctions and was presented to the UN Security Council in February 2003. The same year, Wallensteen's edited book on Nobel Peace Prize Laureate Alva Myrdal, Alva Myrdal in International Affairs, was published.

Wallensteen's other research interests include the durability of peace agreements and the impact of preventive measures on the dynamics of disputes and conflicts.