Louis IX (25 April 1214 – 25 August 1270), later canonized as Saint Louis, was the King of France from 1226 to his death. His reign was marked by strong piety.
In 1239, Louis purchased what was believed to be Jesus Christ's crown of thorns from Baldwin II of Constantinople. In order to store them, he commissioned the construction of the Sainte-Chapelle. Louis himself was the only person who held the key to the chapel reliquary containing the crown, and would present the crown to a kneeling congregation on important occassions. His chaplain, Robert de Sorbon, would go on to found the College of Sorbonne. During his reign, Louis created various provosts, including the Provost of the Merchants in 1246.
Following his death, Louis was buried at the royal crypt in Saint-Denis, and was canonized in 1297. By 1794, a manuscript written by Nicolas de Condorcet had been hidden in Louis' tomb, until it was stolen by the local thief Léon. A piece of Louis' skull was also stolen by a man named Brulay, who sold it at auction.