Religious experiences are usually private though occasionally they are intersubjective, involving multiple individuals at the same time. These group experiences carry extra evidential weight. But what of mass religious experiences, in which hundreds or even thousands of people apparently experience the same supernatural occurrence at the same time? Such events are rare historically, but of great interest in evidential terms, since they are more difficult to explain scientifically. The largest mass religious experiences in recorded history (outside Scripture) occurred over the course of several years in Zeitoun, Egypt. Beginning in 1968, the Virgin Mary began to appear above a Coptic Orthodox Church. These apparitions soon attracted massive crowds and sparked official inquiries by both the Egyptian government and the Coptic hierarchy. This book explores the history of these fascinating events and critically examines every scientific explanation thus far put forward in an attempt to account for them in naturalistic terms. The author argues that, so far, these attempts have failed, and thus the Marian apparitions at Zeitoun constitute powerful evidence for the reality of the supernatural.