A. E. Housman's five-volume critical edition of Marcus Manilius's Astronomicon has long been regarded as the definitive work on the subject. The task of bringing the edition together was one of considerable proportion which took Housman twenty-seven years to complete. It is now considered one of his most enduring and important contributions to scholarship. This volume contains the Latin text of the first book of Manilius, originally published in 1903, and then reissued in a second edition by the Cambridge University Press in 1937. It offers a short introductory note by Housman's friend and colleague at Trinity College, Cambridge, A. S. F. Gow, as well as a detailed introduction by Housman himself, tracing the manuscript history of the work and discussing particular challenges posed by the editorial process.