Napoléon François Charles Joseph Bonaparte (20 March 1811 – 22 July 1832), Prince Imperial, King of Rome, Prince of Parma, Piacenza and Guastalla, known in the Austrian court as Franz from 1814 onward, Duke of Reichstadt from 1818, was the son of Napoleon I, Emperor of the French, and his second wife, Archduchess Marie Louise of Austria.By Title III, article 9 of the French Constitution of the time, he was Prince Imperial, but he was also known from birth as the King of Rome, which Napoleon I declared was the courtesy title of the heir apparent.