The history of psychiatry has over the past decades been largely dominated by the production and re-production of national narratives in which different aspects of psychiatry are often associated with a particular country or region. While this has left little room to consider the value of psychiatry’s less prominent developments, this persistent national tendency has also minimised the role and (in)direct contributions of foreign alienists on national and transnational developments across Europe. Numerous alienists in the nineteenth and early twentieth century strived towards the common goal of better patient care and treatment, and frequently communicated with each other in a variety of ways about these principals and the obstacles they faced. This begs the question if these shared ideals created an imagined or tangible Republic of Alienists, analogue to that of the Republic of Letters. This idea stands in contrast to nationally contained histories and creates the need for new representations of psychiatric knowledge development and its circulation. Transnational narratives can help to decentralise and open-up European historiography, and explore new avenues of the history of psychiatry. Via several case studies and by using concepts, theories and practices from the field of transnational history, the history of knowledge and digital history, I demonstrate the variety of ways through which knowledge was transported and able to circulate across Europe. Secondly, I illustrate that knowledge was built through peoples’ personal and professional networks and reputation, which were shaped by their involvement in various activities in the psychiatric community and through the rhetoric they used to communicate. Thirdly, I explain and highlight the many grey areas that existed in connection to the, not so straightforward, dissemination of psychiatric knowledge. Lastly, I demonstrate that forgotten or failed psychiatric knowledge forms as much a part of history as those facts, events and processes that have been identified as the most essential narratives. Combined, these outcomes demonstrate that there was not just one Republic of Alienists but that several existed in a variety of sizes and different degrees of authority.