This chapter discusses the historical perspectives of abnormal behavior. It covers how abnormality has been defined and understood by ancient societies, Greek thinkers, medieval and Renaissance scholars. It also addresses the development of early asylums and reforms, as well as the foundation of modern abnormal psychology through researchers like Kraepelin and Freud. The chapter concludes by noting abnormal behavior results from both psychological and biological factors and can be studied scientifically while recognizing individual uniqueness.