Who was hiding behind the “iron mask”, the most famous prisoner of France of Louis XIV? Who decided to isolate this man by depriving him of all contact and all outings? What serious fault, what crime did he commit to suffer this punishment that no one before him had received? Writers like Voltaire, Alexandre Dumas or Marcel Pagnol have largely contributed to forging the legend. No less than 50 hypotheses exist on the identity of the man who hides behind this emblematic mask. Alternately, we evoke an overly imposing lover, a hidden son, an overly greedy minister, or even a twin brother of royal blood, who might have ambitions.