This book aims to present an up-to-date introduction and critical study of one of the most important psychoanalysts of all times, Sándor Ferenczi. The book presents Ferenczi as a person; his discovery of psychoanalysis and his relationship with Freud; the theoretical and clinical novelties he introduced to psychoanalysis; his deep political and social commitment, striving for the democratization of psychoanalysis; and the great relevance of his thought and perspective for the future. It also talks about his repression in the history of psychoanalysis as well as his influence in the following generations of psychoanalysts. The reader will be presented with the most relevant historical milestones and concepts, with new insights regarding some of Ferenczi's most fundamental ideas (such as his trauma theory, his technical innovations or his developments regarding the end of analysis), as well as an informed viewpoint of his legacy, the contemporary readings of his work and the institutions and associations that continue following the path traced by l'enfant terrible of psychoanalysis. This book will be of interest both for the novel reader who has had none or scarce contact with the person and/or work of Sándor Ferenczi, as well as to the psychoanalysts, clinicians and scholars, who have a deeper contact and understanding of the work of the Hungarian analyst.