The man in the iron mask, French l’homme au masque de fer, (born c. 1658?—died November 19, 1703, Paris, France), political prisoner, famous in French history and legend, who died in the Bastille in 1703, during the reign of Louis XIV. There is no historical evidence that the mask was made of anything but black velvet (velours), and only afterward did legend convert its material into iron.

He was first imprisoned at Pignerol (Pinerolo, in Piedmont) sometime before 1681, then at other prisons before finally being transferred to the Bastille in Paris on September 18, 1698. He died there on November 19, 1703. Buried the next day in the parish cemetery of Saint-Paul, he was registered there under the name of “Marchioly,” and his age was given as “about 45.” His several moves during his lifetime corresponded with the successive postings of the prison governor Bénigne d’Auvergne de Saint-Mars, in whose charge he was evidently especially committed.

The identity of the man in the mask was already a mystery before his death, and, from the 18th century on, various suggestions as to his identity were made: in 1711, an English nobleman; in 1745, Louis de Bourbon, comte de Vermandois, a son of Louis XIV and Louise de La Vallière; between 1738 and 1771, an elder brother of Louis XIV (Voltaire popularized this unlikely solution, which was later taken up by Alexandre Dumas in Dix Ans plus tard ou le Vicomte de Bragelonne [1848–50], translated into English as The Man in the Iron Mask); in 1883 Molière, imprisoned by the Jesuits in revenge for Tartuffe. Of the dozen or more hypotheses, only two have proven tenable: those for Ercole Matthioli and for Eustache Dauger.

Matthioli, a minister of Ferdinand Charles, duke of Mantua, had been entrusted with the secret negotiation of the treaty of 1678 whereby the impoverished duke was to deliver the stronghold of Casale over to France in return for 100,000 écus, but, as soon as the agreement was signed, Matthioli nullified its effect by betraying the secret to several foreign courts. Furious at having been tricked, Louis XIV had him quietly abducted and imprisoned at Pinerolo (1679). It is generally agreed, however, that Matthioli died in the Îles Sainte-Marguerite in April 1694 and that the prisoner in the mask was Eustache Dauger.

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The correspondence of Louis XIV’s minister Louvois indicates that Dauger, a valet, was arrested on his orders for an unknown reason near Dunkirk in July 1669. At Pinerolo Dauger served as the valet of another prisoner, Nicolas Fouquet, and after Fouquet’s death in 1680 he was kept in close confinement with another man who had also served Fouquet. From Pinerolo, Saint-Mars took him in 1681 to Exilles (whereas Matthioli then stayed behind), before moving to the Îles in 1687. It is possible that Louvois, an enemy of Fouquet, wanted these prisoners kept in custody, lest they should divulge secrets that Fouquet could have told them. Perhaps this consideration, rather more than his original crime, explains the absolute secrecy to which Dauger was condemned and the precaution of the mask.