This article memorializes Peter M. Lewinsohn (1930-2022). Pete pioneered the development of a cognitive behavioral treatment of depressed individuals and research on its efficacy. With his graduate students, he created the Coping With Depression Course, which has been translated into many languages, adapted for older adults and adolescents, and used around the world. This approach is embodied in behavioral activation, a widely used, highly effective treatment of depression. He was a pioneer in translating cognitive behavioral mechanisms into bibliotherapy, including Control Your Depression, a self-help book still in print and used to guide treatment. Pete and colleagues also conducted one of the most comprehensive longitudinal studies on psychopathology, encompassing adolescence and early adulthood. (PsycInfo Database Record (c) 2023 APA, all rights reserved).