The use of Church Slavonic and other Slavic-based language varieties by Romanian-speaking populations in Wallachia, Moldavia, and Transylvania during the late Middle Ages and Early Modern Period represents a fascinating and often overlooked chapter in Slavic philology. This three-volume work explores the evolution and variability of Slavonic writing across the territories of present-day Romania and the Republic of Moldova, shedding light on its interactions with other languages of the region. Spanning from the earliest local Old Church Slavonic inscriptions to the activities of the monastic community of Paisij Velyčkovs’kyj, this work offers a comprehensive perspective on a unique linguistic and cultural phenomenon.