The study of diplomacy has long been centered around the architecture of states and their external interactions, yet rapid societal transformations are reshaping its foundations. The increasing politicization of foreign policy, the rise of populism, and the growing weight of public concerns in global governance are among the forces challenging the traditional separation between the domestic and international spheres. We introduce the concept of the societization of diplomacy to describe this shift and its significance, illustrating how diplomatic practice is rooted in evolving state-society dynamics that cross borders. Introducing the social contract as a first reference, diplomacy emerges not so much as a tool of statecraft but as a practice significantly influenced by citizens’ expectations of legitimacy, representation, and participation. Society is no longer peripheral—if it ever was—and now plays a central role in shaping diplomacy, requiring recognition both in theory and practice. This reconceptualization expands the scope of diplomatic studies, incorporating insights from political theory, sociology, and other social sciences to better understand diplomacy as a governing practice. Ultimately, the societization perspective redefines diplomacy as a collaboratively produced effort where the state and society are deeply interconnected, continuously negotiating interests, the meaning and purposes of foreign policy, and global responsibilities.