This dissertation examines the visual culture of early modern East Slavic presence in Italy, to the extent it was possible to reconstruct it from the dispersed and diverse textual and visual evidence, and locates it within the urban contexts of Rome, Venice, and Naples. At the center of this inquiry is a national church of the Ruthenian (and later Ukrainian) Catholics in Rome since the seventeenth century, Saints Sergio e Bacco, with its miraculous icon of the Madonna del Pascolo.The founding of a Ruthenian national church in Rome, specifically dedicated to the celebration of the Byzantine Rite in Church Slavonic, created a cultural and religious foothold for Eastern European Slavs from the Polish-Lithuanian Commonwealth in the center of the rapidly expanding Global Catholicism. The establishment of the Ruthenian national church in Rome in the old church of Santi Sergio e Bacco in 1639 and papal beatification of the first martyr of the Union – Josaphat Kuncewicz (c. 1580-1623) in 1643, formed an unprecedented opportunity for Ruthenian religious culture to be (re)integrated into Western European at the very height of cultural dominance of the Roman Baroque paradigm. Combining archival documentation, architectural and urban sites, and a diverse selection of prints, maps, books, and paintings, the dissertation examines the groundwork of this cultural integration, the specific developments in ecclesiastical culture in the wake of the Ruthenian incorporation among the already well established nationes of the Eternal City, and the formation of a recognizably new Ruthenian culture marked by what we now consider as the Baroque aesthetic.