This part presents the first comprehensive critical edition of the Office for Saint Wenceslas, based on all surviving manuscript witnesses: three East Slavic manuscripts from the Novgorod area dating from the late 11th and 12th centuries. Previous editions of the text, though numerous, were largely diplomatic and lacked a systematic critical assessment of the manuscript tradition. Two main branches are identified, one represented by manuscript T and the other by the closely related Sin and Sof. The edition adopts Sin as the base text because of its neumatic notation, which aids metrical reconstruction. Editorial principles, conjectural emendations, and variant readings are carefully documented in a full critical apparatus. The volume also includes Greek parallels, an Italian service translation, and comparative material from modern Church Slavonic editions of the Menaion.