Napoléon François Joseph Charles Bonaparte (20 March 1811 – 22 July 1832), Prince Imperial, King of Rome, known in the Austrian court as Franz from 1814 onward, Duke of Reichstadt from 1818, was the son of Napoleon, Emperor of the French, and his second wife, Archduchess Marie Louise of Austria.
At the time of his birth, by Title III, article 9 of the French Constitution, 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.
His nickname of L'Aiglon ("the Eaglet") was awarded posthumously and was popularized by the Edmond Rostand play, L'Aiglon.
When Napoleon I tried to abdicate on 4 April 1814, he said that his son would rule as emperor.
However, the coalition victors refused to acknowledge his son as successor, and Napoleon I was forced to abdicate unconditionally some days later.
Although Napoleon II never actually ruled France, he was briefly the titular Emperor of the French in 1815 after the second fall of his father.
When his cousin Louis-Napoléon Bonaparte became the next emperor by founding the Second French Empire in 1852, he called himself Napoleon III to acknowledge Napoleon II and his brief reign.