Robert J. MacCoun (born October 18, 1958) is the James and Patricia Kowal Professor of Law at Stanford Law School.,[1] a Professor by courtesy in Stanford's Psychology Department, and a senior fellow at the Freeman Spogli Institute.

Trained as a social psychologist, he has published numerous studies on psychoactive drug use and policy, individual and group decision-making, distributive and procedural justice, social influence processes, and bias in the use and interpretation of research evidence by scientists, journalists and citizens.

In 2019, MacCoun received the James McKeen Cattell Fellow Award of the Association for Psychological Science, which “honors distinguished APS Members for a lifetime of outstanding contributions to applied psychological research.”[2] He served as Editor of the Annual Review of Law and Social Science from 2018-2021.

His co-authored book with physicist Saul Perlmutter and philosopher John Campbell, Third Millennium Thinking: Creating Sense in a World of Nonsense, was published by Little, Brown Spark in 2024.

In 1999, he came to Princeton University as a Visiting Professor to design and launch a graduate course on psychology and public policy with Daniel Kahneman and Eldar Shafir.