The Holy Grail (French: Saint Graal, Breton: Graal Santel, Welsh: Greal Sanctaidd, Cornish: Gral) is a treasure that serves as an important motif in Arthurian literature. Various traditions describe the Holy Grail as a cup, dish, or stone with miraculous powers: providing eternal youth, or sustenance in infinite abundance, often in the custody of the Fisher King. By analogy, any elusive object or goal of great significance may be perceived as a holy grail by those seeking it.
A "grail", wondrous but not unequivocally holy, first appears in Perceval, le Conte du Graal, an unfinished romance written by Chrétien de Troyes around 1190. Chrétien's story attracted many continuators, translators and interpreters in the later 12th and early 13th centuries, including Wolfram von Eschenbach, who perceived the Grail as a stone. In the late 12th century, Robert de Boron wrote in Joseph d'Arimathie that the Grail was Jesus's vessel from the Last Supper, which Joseph of Arimathea used to catch Christ's blood at the crucifixion. Thereafter, the Holy Grail became interwoven with the legend of the Holy Chalice, the Last Supper cup, a theme continued in works such as the Lancelot-Grail cycle and consequently Le Morte d'Arthur.
In 1818, Austrian pseudohistorical writer Joseph von Hammer-Purgstall connected the Grail to contemporary myths surrounding the Knights Templar that cast the order as a secret society dedicated to mystical knowledge and relics.
In the late 20th century, writers Michael Baigent, Richard Leigh and Henry Lincoln created one of the most widely known conspiracy theories about the Holy Grail. The theory first appeared in the BBC documentary series Chronicle in the 1970s and was elaborated upon in the bestselling 1982 book Holy Blood, Holy Grail. The theory combines myths about the Templars and Cathars with various other legends and a prominent hoax about a secret order called the Priory of Sion. According to this theory, the Holy Grail is not a physical object, but a symbol of the bloodline of Jesus. The blood connection is based on the etymological reading of san greal (holy grail) as sang real (royal blood), which dates to the 15th century. The narrative developed here is that Jesus was not divine, and had children with Mary Magdalene, who took the family to France, where their descendants became the Merovingians dynasty. While the Catholic Church worked to destroy the dynasty, they were protected by the Priory of Sion and their associates, including the Templars, Cathars, and other secret societies. The book, its arguments, and its evidence have been widely dismissed by scholars as pseudohistorical, but it has had a vast influence on conspiracy and alternate history books. It has also inspired fiction, most notably Dan Brown's 2003 novel The Da Vinci Code and its 2006 film adaptation.