The Prieuré de Sion, usually rendered in English translation as Priory of Sion (occasionally as 'Priory of Zion'), is an alleged thousand-year-old cabal featured in various conspiracy theories, as well as being listed as a factual ancient mystery religion in the best-selling novel The Da Vinci Code by Dan Brown. It has been characterized as anything from the most influential secret society in Western history to a modern Rosicrucian-esque ludibrium, but, ultimately, has been shown to be a hoax created in 1956 by Pierre Plantard, a pretender to the French throne. The evidence presented in support of its historical existence is not considered authentic or persuasive by established historians, academics, and universities, and the evidence was later discovered to have been forged and then planted in various locations around France by Plantard and his associates. Nevertheless, many conspiracy theorists insist on the truth of the Priory's role as a powerful secret society. 
The actual Priory
The real Priory of Sion is an association that was founded in 1956, in the French town of Annemasse, as the beginning of a massive hoax.
As with all associations, French law required that the association be registered with the government. It was registered with its Statutes at the Sub-Prefecture of Saint Julien-en-Genevois, in May 1956, and its registration was noted on 20 July 1956, in the Journal Officiel de la République Française. The founders and signatories are inscribed with their pseudonyms as Pierre Plantard (known as "Chyren"), André Bonhomme (known as "Stanis Bellas"), Jean Delaval, and Armand Defago. The purpose of the association according to its Statutes was entered as, "Études et entraide des membres" ("Studies and mutual aid of the members"). In practice, the originator of the association and its key protagonist was Pierre Plantard, its General Secretary, although its nominal head ("President") was André Bonhomme. The choice of the name, "Sion" was based on a popular local feature, a hill south of Annemasse in France, known as 'Mont Sion'.. The accompanying title, or subtitle to the name was, Chevalerie d'Institutions et Règles Catholiques d'Union Independante et Traditionaliste: this forms the acronym CIRCUIT and translates as "Knighthood of Catholic Rule and Institution and of Independent Traditionalist Union."
The Statutes and Registration Documents of the Priory of Sion were deposited on 7 May 1956, while the first issue of its journal Circuit is dated 27 May 1956 (in total, twelve numbers of the journal appeared). Considering the political instability of the French Fourth Republic, the objectives of the journal were regarded with suspicion by the local authorities. It was indicated as a "Bulletin d'Information et Défense des Droits et de la Liberté des Foyers HLM" ("News Bulletin for the Defence of the Rights and the Freedom of Council Housing"). Indeed, some of the articles took a political position in the local Council elections. Others attacked and criticized property developers of Annemasse. It also opposed the gentrification of the area. The offices of the Priory of Sion and the journal were at Plantard's council flat.
The articles of the Priory of Sion as indicated in its Statutes also desired the creation of a monastic order, but the activities of the Priory of Sion bore no resemblance whatsoever to the objectives as outlined in its Statutes. Article VII says that its members are expected, "to carry out good deeds, to help the Roman Catholic Church, teach the truth, defend the weak and the oppressed". There is ample evidence that it had several members, as indicated by the numerous articles contained in its journal Circuit, written by a number of different people. Towards the end of 1956 the association had aims to forge links with the local Catholic Church of the area involving a school bus service run by both the Priory of Sion and the church of St Joseph in Annemasse.
Plantard hoped that the Priory of Sion would become an influential cryptopolitical irregular masonic lodge (similar to P2) dedicated to the restoration of chivalry and monarchy, which would promote Plantard's own claim to the throne of France.
Between 1961 and 1984 Plantard contrived a mythical pedigree of the Priory of Sion claiming that it was the offshoot of the monastic order housed in the Abbey of Sion, which had been founded in the Kingdom of Jerusalem during the First Crusade and later absorbed by the Jesuits in 1617. The mistake is often made that this Abbey of Sion was a "Priory of Sion", but there is a difference between an abbey and a priory. Calling his
original 1956 group "Priory of Sion" presumably gave Plantard the later idea to claim that his organization had been historically founded in Jerusalem during the Crusades.
Proof of the conspiracy
Letters in existence dating from the 1960s written by Plantard, de Cherisey and de Sède to each other confirm that the three were engaging in an out-and-out confidence trick, describing schemes on how to combat criticisms of their various allegations and how they would make up new allegations to try and keep the whole thing going. These letters (totalling over 100) are in the possession of French researcher Jean-Luc Chaumeil, who has also retained the original envelopes. Jean-Luc Chaumeil during the 1970s was part of the Priory of Sion cabal, and wrote books and articles about Plantard and the Priory of Sion before splitting from it during the late 1970s and exposing Plantard's past in French books.
A letter later discovered at the Sub-Prefecture of St. Julien-en-Genevois also indicated that Plantard had a criminal conviction as a con man.
The disposition of the "real" Priory
The formally registered association was dissolved sometime after October 1956 but intermittently revived for different reasons by Plantard between 1962 and 1993, though in name and on paper only. The Priory of Sion is considered "dormant" by the Sub-Prefecture because it has indicated no activities since 1956. According to French law, subsequent references to the Priory bear no legal relation to that of 1956 and no one other than the original signatories are entitled to use its name in an official capacity. André Bonhomme played no part since 1956. He officially resigned in 1973 when he heard that Plantard was linking his name with the association, so as of last report, there is no one who is currently around who has official permission to use the name.
The Holy Blood and the Holy Grail
After reading Le Tresor Maudit, Henry Lincoln persuaded BBC Two's factual television series of the 1970s Chronicle to make a series of documentaries, which became quite popular and generated thousands of responses. Lincoln then joined forces with Michael Baigent and Richard Leigh for further research. This led them to the pseudohistorical Dossiers_Secrets at the Bibliothèque nationale, which though alleging to portray hundreds of years of medieval history, were actually all written by Plantard and de Cherisey under the pseudonym of "Philippe Toscan du Plantier". Unaware that the documents had been forged, Baigent, Leigh and Lincoln used them as a major source for their book, The Holy Blood and the Holy Grail, in which they declared as "fact" that:
The Priory of Sion has a long history starting in AD 1099, and had illustrious Grand Masters including Isaac Newton and Leonardo da Vinci (see full list below);
the Knights Templar were created as the military and financial front of the Priory;
it is sworn to returning the Merovingian dynasty, that ruled the Franks until 751 AD, to the thrones of Europe and Jerusalem;
the order protects these royal claimants because they believe them to be the literal descendants of Jesus and his alleged wife Mary Magdalene or, at the very least, of king David;
the Roman Catholic Church tried to kill off all remnants of this dynasty and their guardians, the Cathars and the Templars, in order to maintain power through the apostolic succession of Peter instead of the hereditary succession of Mary Magdalene.
The authors further asserted that the ultimate goals of the Priory of Sion are:the founding of a "Holy European Empire" that would become the next hyperpower and usher in a new world order of peace and prosperity;
the establishment of a messianic mystery state religion by revealing the Holy Grail;
the grooming and installing of a "Rex Deus" pretender on the throne of a Greater Israel.
Baigent, Leigh, and Lincoln even incorporated the infamous anti-semitic tract known as The Protocols of the Elders of Zion into their story, concluding that it actually referred to the activities of the Priory of Sion. Regarding the Protocols, they mistakenly viewed this as the most persuasive pieces of evidence for the existence and activities of the Priory of Sion:
The original version emanated from an irregular Masonic organization that used the name "Sion" but had nothing to do with an international Jewish conspiracy.
The original version was not intended to be inflammatory or released publicly, but was a program for gaining control of Freemasonry.
The person responsible for changing the text in about 1903 was Sergei Nilus in the course of his attempt to gain influence in the Court of Tsar Nicholas II of Russia. The presence of esoteric cliques in the royal court led to considerable intrigue. Nilus' publication of the text resulted from his failure to succeed in wresting influence away from Papus and an otherwise unidentified "Monsieur Philippe".
Since Nilus did not recognize a number of references in the text that reflected a background in a Christian cultural context, he did not change them. This fact established that the original version could not possibly have come from the first Zionist Congress in Basel (1897).
Accepting these factoids as the truth, some fringe Christian eschatologists viewed the Priory of Sion as a fulfillment of prophesies found in the Book of Revelation and further proof of an anti-Christian conspiracy of epic proportions.
However, modern historians do not accept The Holy Blood and the Holy Grail as a serious contribution to scholarship and regard all these claims as being part of a dubious conspiracy theory. French authors like Franck Marie (1978), Jean-Luc Chaumeil (1979, 1984, 1992, 2006) and Pierre Jarnac (1985, 1988) and more recently Marie-France Etchegoin (2004), Massimo Introvigne (2005), Jean-Jacques Bedu (2005), have never taken Pierre Plantard and the Priory of Sion as seriously as Baigent, Lincoln and Leigh. They eventually concluded that it was all a hoax, outlining in detail the reasons for their verdict, and giving detailed evidence that the Holy Blood authors had not reported comprehensively. They imply that this evidence had been ignored by Baigent, Lincoln and Leigh in order to bolster the mythic version of the Priory's history that was developed by Pierre Plantard during the early 1960s after meeting author Gérard de Sède.
In 1989, Pierre Plantard tried but failed to salvage his reputation and agenda by claiming that the Priory of Sion had actually been founded in 1681 at Rennes-le-Château.
The Pelat affair
In September 1993, Plantard approached of his own volition an investigative judge, Thierry Jean-Pierre who, at the time, was investigating the activities of multi-millionaire Roger-Patrice Pelat. Plantard communicated to the judge that the man he was investigating had once been grandmaster of the Priory of Sion. Indeed, Pelat's name had been on Plantard's list of grandmasters since 1989. In fact, Pelat had died in 1989, while he was being indicted for insider trading - or délit d'initié in French. Plantard was not only naive about French law but also of financial terms and he interpreted the word "initié" esoterically, to mean "initiate". Following a long established pattern, Plantard "recruited" the "initiate" Pelat soon after his death and included him as the most recent Priory of Sion grandmaster.
But in 1993, Plantard failed once more to realise the severity of interfering with the law; he had made his most important mistake and it led to his eventual isolation. Pelat had been a friend of François Mitterrand, then President of France, and at the centre of a scandal involving French Prime Minister Pierre Bérégovoy. As an investigative judge, Thierry Jean-Pierre could not dismiss any information pertaining to his case that was brought to his attention, but since he never considered it worthwhile meeting Plantard, he ordered the search of Plantard's home by his officers.
This turned up what has been described as a fantasy-land of harmless, forged documents, including some proclaiming Plantard the true king of France. Under oath, Plantard had to admit that he had fabricated everything, including Pelat's involvement with the Priory of Sion. Plantard was ordered to cease and desist all activities related to the promotion of the Priory of Sion and lived in obscurity until his death on 3 February 2000, in Paris.
The alleged "relaunch" of the Priory
On 27 December 2002, a letter was released on "official" Priory stationery announcing a public relaunch of the fraternity. It was signed by someone claiming to be Plantard's former private secretary, Gino Sandri under the title of General Secretary, and an unnamed woman as "President" («Nautonier» - an Old French word for a navigator and which means Grand Master in the Priory esoteric nomenclature).
The Da Vinci Code
Recently, as a result of Dan Brown's best-selling novel The Da Vinci Code and the movie made from it, there has been a new level of public interest in the Priory of Sion. Brown's novel promotes the mythical version of the Priory: it was founded in 1099, Leonardo da Vinci, Victor Hugo, Robert Boyle, and Sir Isaac Newton were among its Grand Masters, etc. The author has presented this as fact in a non-fiction preface, public appearances, and interviews.
The Sion Revelation
Further conspiracies are alleged in The Sion Revelation: The Truth About the Guardians of Christ's Sacred Bloodline (2006) by Lynn Picknett and Clive Prince (authors of the 1997 book The Templar Revelation, the principal source for Dan Brown's claims about hidden messages in the work of Leonardo da Vinci). They accept the evidence that the Priory was created by Plantard, and that its pre-1956 history is fraudulent, but they insist that this was a part of a complex double-bluff designed to discredit the story of the "divine bloodline" and the secret organizations that support it. They argue that these plotters are attempting to create a United States of Europe.