The authors retrace the various stages of the birth of the Société Médico-Psychologique (SMP), which celebrated its 170th anniversary in 2022. They recall the context, notably a law enacted in 1838 that was considered as a foundation text for what was then called alienism and which would eventually become psychiatry. The work of Philippe Pinel and Jean Étienne Esquirol played an essential role in the founding of the SMP, and more broadly in the genesis of the discipline. Three phases can be distinguished in the foundation of the SMP: (1) the creation of the Annales Médico-Psychologiques (AMP), in 1843, a journal that would become the SMP bulletin; (2) the first constitution of the SMP which was announced by Jules Baillarger in the first issue of the AMP in 1848 and which included the first organizational rules and a first list of members; (3) For political reasons (The revolution of February 1848, a political coup d’état on December 2, 1851), the foundation of the SMP would officially first take place in 1852. A commission of members modified the first internal rules. A principle was established whereby the Society would be composed of physicians, philosophers, magistrates, clergymen, moralists, teachers, poets, etc. The professional journals announced at the time the establishment of a Society where “all the instruments of psychological analysis will be gathered and applied simultaneously”. The first meeting of the Society was held on the 26th of April 1852. The authors provide a list of the founding members, although there were some notable absences. The relations between the SMP and the Academy of Medicine, founded in 1820, are detailed. The first international members are mentioned. They came from The Netherlands, Spain, Italy, Russia, Austria and Germany, and at the end of the 19th century, from America as well During the same time period, similar learned societies were established, notably in the United Kingdom, Germany and Russia. The authors describe in detail the creation of the Association of Medical Superintendents of American Institutions for the Insane (ASAMSAII), the future American Psychiatric Association (APA), and of its Journal which would become the American Journal of Psychiatry. The details of joint meetings between the APA and the SMP in 1978 are reported. The birth of the SMP and of other learned societies in Germany, France and the United Kingdom marked the beginning of a discipline which was then called alienism and which would become Psychiatry.