In this book Napolitano shows the rendering of migration present at the heart of the 21C Roman Catholic Church and why this is a key battleground for a changing Europe. She shows how Catholic Latin American lay and religious migrants and their histories in Rome point to an Atlantic Return from the Americas that challenges an Euro-centric, Roman Catholic identity. She queries national, municipal histories and Vatican pastoral teachings through documented and undocumented migrants’ experiences and devotions and shows how multiple forms of being Catholic inform gender, labour and sexuality at the heart of Catholicism in Europe. By studying present celebrations of the Virgin of Guadalupe and El Señor de los Milagros, Papal Encyclicals, the Latin American Catholic Mission and the order of the Legionaries of Christ in Rome she bridges the long-standing divide between the study of popular and institutional Catholicism, and between current circulations of affects around migration in Italy and the Catholic Church’s historical anxieties and hopes of conversion since the early missionization of the Americas. Through an Atlantic and transnational perspective Napolitano shows how the Roman Catholic Church is a passionate machine, an ethical and political subject that reignites a passion for Catholicism based on one hand on Papal liturgy and the importance of the moral truth, and on the other on how diverse Catholic migrants can become an apostolic vessel for new blood in a Europe perceived as having cooled to the Catholic faith.