Despite the recent outpouring of scholarship on Piers Plowman, Lawrence Warner contends, we know much less about the poem's production, transmission, and readership than one might think. When did William Langland write each of the three versions of the poem, and when did they enter wide circulation? What role did scribes and other agents play in these processes? The Lost History of "Piers Plowman" engages with these questions to bring about a fundamental shift in our understanding of the genesis and development of the Middle English poem. According to received history, the poem exists in three distinct, chronological versions, the A, B, and C texts, with most scholars agreeing that Langland completed the B text—the version most familiar to modern readers—around 1377-78. Challenging much of the prevalent wisdom about the poem, Warner argues that the received B text is not an integral poem aligned with a single author but, rather, two groups of manuscripts, each of which, because of scribal activities, takes on varying amounts of what we now call C version matter. Through close textual analysis, he reveals that the B text is a conflation of an ur-B text with a collection of passages that belong to the C version of circa 1390, demonstrating that the circulation of the C text actually predates that of the B. The Lost History of "Piers Plowman" is a groundbreaking and provocative work that establishes an entirely new paradigm for the study of one of the central works of Middle English literature. It will be of interest to scholars and students of textual studies, editorial theory, and medieval history.