From October 1428 to May 8, 1429, a battle ensued in the city of Orleans, France, which turned the tide of the Hundred Years' War. This French victory, led by Jehanne la Pucelle, inspired a dismayed and bankrupt army to finally regain the throne from English usurpers. The Mistere du siege d'Orleans recounts this victory in a sweeping panorama encompassing English plans to take Orleans, the nine-month battle which followed, and the skirmishes which forced the English to flee the area. Intrinsic to this play is the lesson in humility before God which Jehanne personifies. Yet this mystere, which recounts in a precise and accurate manner these decisive and well-known contemporary events, is nowhere mentioned in fifteenth-century writings. The single manuscript yielded a lone edition until the present day, and research on the work has been minimal. Our edition rectifies the numerous errors in the nineteenth-century edition and reproduces the early sixteenth-century copy of the manuscript. Also included are chapters dealing with historical sources, dramatic and thematic natures, and the origins of this work. Since the manuscript is anonymous, discussion as to its composition has centered on a possible compilation of various parts of the Siege. Such a solution may explain difficulties in dating the manuscript and in determining its author or authors. We review the likelihood of a compilation by studying aspects of the work in this light, together with our own analyses of details of the Siege and their relevancy to other fifteenth-century documents. By defining the Mistere du siege d'Orleans in this manner, we hope to rekindle interest in this popular, dramatic creation.