The Poet’s Matere: Materiality, Temporality, and the Making of Literary History in Chaucer and Lydgate’s Inset-Lyric Poems proposes a new conceptual framework for understanding how medieval poets conceptualized their relationship to the literary past and demonstrates how that conceptualization resulted in metapoetic theorizations having to do with literary history and the making of poetry. Across the inset-lyric poems of the fourteenth-century English poet Geoffrey Chaucer and his fifteenth-century successor John Lydgate, I track how these poets take up, elaborate, and complicate a theory of literary matere (or “matter”) which shows close ties to, but also moves beyond what is meant in modern theoretical discourses about materiality. Examining interstitial moments where shorter lyrics are stitched into the fabric of a longer poetic narrative, I contend that at these fissures Chaucer and Lydgate develop a capacious concept of literary matere that traverses the terrain between the concrete and the abstract, the material and immaterial. Matere thus encompasses subject matter, theme, form, and the physical vehicles of textual transmission: books and scraps of parchment, as well as textiles, buildings, monumental inscription, stained glass, and even song. The embedded lyric they imagine as a physical fragment whose presence implies a sense of poetry as an assemblage of physical materials collected from the past, and poets as the collectors and mediators of those materials. The complex sense of literary matere that Chaucer and Lydgate bring to English poetics eventually comes to influence how Elizabethan antiquaries—also collectors of artefacts and antiquities— repackage medieval poetry in Renaissance anthologies. The Poet’s Matere not only uncovers the implications of medieval material poetics for the Renaissance reception of medieval literature, but also shows how the materiality of poetry continues to shape our reading and interpretation of English literature in the modern university.