Transnational history refers to a body of historiographical work that departs from nation-state-centered narratives and instead emphasizes circulation, cooperation, contact zones, and cross-border interactions and transits. It focuses on analyses that reveal how movements, exchanges, and connections unfolded across national boundaries. The text begins by examining how psychology and madness became subjects of historical and interdisciplinary inquiry, highlighting key historiographical shifts introduced by the nouvelle histoire and by authors such as Michel Foucault and Peter Gay from the 1960s onwards. These developments took shape within broader transformations in historical theory and writing, which facilitated both a closer engagement between psychology and history and the emergence of transnational approaches. Therefore, the chapter also surveys current research trends that combine history and psychology through a transnational lens and addresses emerging innovative perspectives on the history of psychology within this historiographical framework.