Middle English literature is intimately concerned with sleep and the spaces in which it takes place. In the medieval English imagination, sleep is an embodied and culturally determined act, subject to a particular habitus and understood through particular hermeneutic lenses. An examination of sleep can shed light on what it enables (dreams and dream poetry) and what it stands in for or supersedes (desire and sex). This book argues that sleep mediates thematic concerns in ways that have ethical, affective, and oneiric implications. At the same time, it offers important contributions to understanding different Middle English genres: romance, dream vision, drama, and fabliau. While concentrating on the fourteenth and fifteenth centuries, the book attends to a longue durée in the literature about sleep circulating from the twelfth century to the early seventeenth. It focuses on continuities in the construction of sleep across this period - scientific, social, spiritual, and spatial - and explores the cultural specificity of premodern English literature's widespread interest in the subject. Analysing how representations of sleep animate ethical codes and emotive scripts, Sleep and its spaces in Middle English literature demonstrates the significance of sleep-related motifs to Middle English romance and offers a more embodied understanding of dream visions by Chaucer, Langland, and the Pearl-poet.