“The Twenty-five Joys of Our Lady” is a study, examination, and critical edition of an unpublished fifteenth-century Middle English prose devotion preserved in Bodleian Library MS Don. d. 85. It is here associated with twenty-five “Joys of Our Lady” and presented as a vernacular Marian rosary, the first such to be identified in the period. The introduction to the edition considers early liturgical influences upon what became the tradition of Our Lady’s Joys, their late-medieval development both across Europe and across England, and the circumstances that usually indicated fewer in number than is present in the devotion printed here. The introduction also concerns itself with the presence and practice of the rosary itself in late-medieval England and elsewhere and the limited evidence that has come down to us for its presence and circulation in England, including woodcut evidence in Caxton and allusions in other Latin devotions. It further indicates an ambiguity in this devotion’s treatment of Christ’s passion and concludes by considering the role and importance of joy as a pervasive, if often ignored, Christian attitude present in late-medieval English devotion.