The John Mack Institute (JMI) is a 501(c)(3) nonprofit based in Cambridge, Massachusetts, and named for the Pulitzer Prize-winning Harvard psychiatrist John E. Mack. It is the working name of the Center for Psychology and Social Change, the organization Mack founded, and it describes itself as a "non-profit home for independent projects dedicated to the evolution of human consciousness." Its stated mission begins "to explore the frontiers of human experience." The institute is best known for carrying on Mack's work with people who report encounters with nonhuman beings, whom it calls experiencers.

According to the institute's own history, Mack and the psychiatrist Robert Jay Lifton founded it in 1982 as the Nuclear Psychology Program, an affiliate of Harvard Medical School. It became independent in 1986 as the Center for Psychological Studies in the Nuclear Age, gained consultative status with the UN Economic and Social Council in 1988 and took the name Center for Psychology and Social Change in 1992, after the Cold War ended. Contemporary Authors gives 1983 as the center's founding year. Its early names reflected Mack's research on the psychology of the nuclear age.

In 1993, with funding from the philanthropist Laurance Rockefeller, the center formed the Program for Extraordinary Experience Research (PEER) at Harvard's Cambridge Hospital to study how reported alien encounters affected people's sense of identity and worldview. PEER sent out an experiencer survey, ran a multiple-witness study and convened a 23-member multidisciplinary meeting at Harvard in April 1999. Its newsletter, PEER Perspectives, reached nearly 10,000 people in the United States and 44 other countries, and its therapist referral network grew to more than 100 licensed clinicians. The program closed in 2002. Its research put the center in the middle of the abduction and contact debate, where critics argued that hypnosis and suggestive interviewing could shape the accounts Mack collected.

After Mack passed away in 2004, the center was renamed in his honor. Its later projects include the Experiencer Disclosure Initiative, begun in 2021 to "establish the credibility of a diverse, international Experiencer community," and an Experiencers of Color Collective formed in 2024. Mack's papers went to Rice University's Center for the Impossible, and in 2024 the institute and Rice announced a two-year study to anonymize and analyze the abduction collections.

Its 2026 leadership includes executive director Andrea Oddo, clinical director Simon Bresler, research director Kimberly S. Engels and managing director Karin Austin, a former participant in Mack's research who also manages the Rice center. On July 10, 2026, the institute and the Rice center held "Breaking the Taboo," a free online symposium on reviving academic research into UAP, abduction and experiencer reports, where Oddo and communications director Charles Holt spoke on helping experiencers through "ontological shock." In October, Austin argued on the Psicoactivo podcast that stigma had kept experiencers out of the disclosure debate. More than two decades after Mack's passing, the institute has added peer support and advocacy for experiencers to the research Mack began, while its partnership with Rice keeps his case files available to researchers.