My dissertation considers the relationship between memory, the highest creative and ethical power in medieval culture, and the visionary narrative, one of the period's most popular literary genres. Reading a variety of visionary narratives (including Chaucer's _House of Fame_ and _The Book of Margery Kempe_), I argue that memoria is crucial not only for understanding the principles that underlie the creation and reception of these texts, but also for understanding their relationship to other literary genres, such as romance and courtly love poetry, as well as to contemporary works of philosophy and theology.