This book tells the story of the experts who sold the idea of Franco's 'social state'. Despite the repression, violence, and social hardship which characterized Spanish life in the 1940s and 1950s, the Franco regime sought to win popular support by promoting its apparent commitment to social justice. This book reveals the vital role which the idea of the social state also played in the regime's ongoing search for international legitimacy. It shows how social experts, particularly those working in the fields of public health, medicine, and social insurance, were at the forefront of efforts to promote the regime to the outside world. By working with international organizations and transnational networks across Europe, Africa, and Latin America, they sought to sell the idea of Franco's Spain as a respectable, modern, and socially just state. In doing so the book also seeks to disrupt our understanding of the modern history of internationalism. Exploring what it meant for Francoist experts to think and act internationally, it challenges dominant accounts of internationalism as a liberal, progressive movement by foregrounding the history of fascist, nationalist, imperialist, and religious forms of international cooperation. The case of Spain reveals the contested and heterogenous nature of mid-twentieth-century internationalism, characterized by the tumultuous interplay of overlapping global, regional, and imperial projects. It also brings into focus the overlooked continuities between international structures and projects before and after 1945.