The present chapter provides a comprehensive overview of the evolution of the bipolar disorder concept from its earliest descriptions in ancient texts to its current understanding as a distinct psychiatric condition. The chapter traces the significant contributions of key figures, such as Aretaeus of Cappadocia, who linked mania and melancholia as part of a single spectrum, and Jean-Pierre Falret and Jules Baillarger, who introduced the concepts of la folie circulaire and la folie à double forme. Building on these ideas, Emil Kraepelin later distinguished manic-depressive insanity from dementia praecox, further refining the nosology. It also discusses the progression of bipolar disorder research into the twentieth century, highlighting the impact of lithium therapy and the debate over the condition’s heterogeneity. Contemporary research advancements, including longitudinal studies, neuroimaging, neurobiology, and the development of treatment guidelines, are also reviewed. The chapter concludes by emphasizing the importance of historical knowledge in shaping current and future approaches to the diagnosis and management of bipolar disorder, noting the contributions of various scholars who have helped to define this complex and multifaceted condition.