Arnold Allan Lazarus (born 27 January 1932 - 1 October 2013) was a South Africanpsychologist who is known for his contributions to behavior therapy. He wrote more than 250 articles and chapters and 18 books, including his classic The Principles of Multimodal Therapy.
From the late 1950s into the 1970s, at the same time that Albert Ellis and Aaron Beck were pioneering cognitive therapy, Lazarus was developing what was arguably the first form of "broad-spectrum" cognitive behavioral therapy. In 1958, he introduced the terms "behavior therapy" and "behavior therapist" (i.e., Lazarus, A. A. "New methods in psychotherapy: a case study". South African Medical Journal, 1958, 32, 660-664).
He later broadened the focus of behavioral treatment to incorporate cognitive and other aspects (e.g., see Arnold Lazarus' 1971 landmark book Behavior Therapy and Beyond, perhaps the first clinical text on CBT). When it became clear that optimizing therapy's effectiveness and effecting durable treatment outcomes often required transcending more narrowly focused cognitive and behavioral methods, Arnold Lazarus expanded the scope of CBT to include physical sensations (as distinct from emotional states), visual images (as distinct from language-based thinking), interpersonal relationships, and biological factors. The final product of Arnold Lazarus' approach to psychotherapy is called multimodal therapy and shares many of its assumptions and theorizing with Ellis' rational emotive behavior therapy.