The Miracle of the Sun (Portuguese: Milagre do Sol), also known as the Miracle of Fátima, is a series of events reported to have occurred miraculously on 13 October 1917, attended by a large crowd who had gathered in Fátima, Portugal, in response to a prophecy made by three shepherd children, Lúcia Santos and Francisco and Jacinta Marto. The prophecy was that the Virgin Mary (referred to as Our Lady of Fátima), would appear and perform miracles on that date. Newspapers published testimony from witnesses who said that they had seen extraordinary solar activity, such as the Sun appearing to "dance" or zig-zag in the sky, careen towards the Earth, or emit multicolored light and radiant colors. According to these reports, the event lasted approximately ten minutes.

The local bishop opened a canonical investigation of the event in November 1917, to review witness accounts and assess whether the alleged private revelations from Mary were compatible with Catholic theology. The local priest conducting the investigation was particularly convinced by the concurring testimony of extraordinary solar phenomena from secular reporters, government officials, and other skeptics in attendance. Bishop José da Silva declared the miracle "worthy of belief" on 13 October 1930, permitting "officially the cult of Our Lady of Fatima" within the Catholic Church.At a gathering on 13 October 1951 at Fátima, the papal legate, Cardinal Federico Tedeschini, told the million people attending that on 30 October, 31 October, 1 November, and 8 November 1950, Pope Pius XII himself witnessed the miracle of the Sun from the Vatican gardens. The early and enduring interest in the miracle and related prophecies has had a significant impact on the devotional practices of many Catholics.There has been much analysis of the event from critical sociological and scientific perspectives. According to critics, the eyewitness testimony was actually a collection of inconsistent and contradictory accounts. Proposed alternative explanations include witnesses being deceived by their senses due to prolonged staring at the Sun and then seeing something unusual as expected.