Mahlon Brewster Smith (June 26, 1919 – August 4, 2012) was an American psychologist and past president of the American Psychological Association. His career included faculty appointments at Vassar College, New York University, University of California, Berkeley, University of Chicago and University of California, Santa Cruz. Smith had been briefly involved with the Young Communist League as a student at Reed College in the 1930s, which resulted in a subpoena by the U.S. Senate in the 1950s. That activity caused him to be blacklisted by the National Institute of Mental Health for ten years without his knowledge.
Smith testified against segregation in schools as an expert witness in the Brown v. Board of Education case; the scope and scientific basis for Smith's testimony have been the subjects of controversy. He was the vice president of the Joint Commission on Mental Illness and Health, the group whose recommendations led to the deinstitutionalization of most of the mentally ill in the United States. In 1961, he helped to interview and select the first group of Peace Corps volunteers.
