Duke Ferdinand of Hungary (19 April 1793 - 29 June 1841) was the son of Francis I of Austria and, between 1814 and 1820, ruled the Duchy of Hungary, a nominally independent French vassal state carved out of the remains of the Austrian Empire after Napoleon annexed large parts of his father's western domains. He was referred to officially and colloquially as "Ferdinand the Austrian" and was recognized by some Hungarians as King Ferdinand V, although he was never officially styled in this manner as Napoleon abolished the crown of Hungary, rendering it a satellite duchy. He was the only of Francis I's children to remain in Europe following Napoleon's conquest of Austria and thus was effectively the last Hapsburg ruler in Europe, although many consider Napoleon's children to technically be Hapsburgs due to the French Emperor's marriage to Marie Louise.
Ferdinand was, by all accounts, an enormously ineffectual ruler, possibly due to genetic deficiencies, his youth and inexperience (he was only 20 years old when given charge of the reeling duchy) and his inability to speak Hungarian. Ferdinand apparently suffered from epilepsy and severe speech impediments, although he did not appear to suffer from any overwhelming mental disorders based on his diaries. However, he never married, and his epileptic seizures kept him from ruling effectively. While he was never declared incapacitated, Napoleon clearly used his feeble-minded rule to his advantage, and Hungary was practically ruled by Louis, a former Austrian archduke and Ferdinand's relative.
After Napoleon's armies stormed Budapest in 1820 and annexed the duchy into the greater French Empire and appointed Louis as the Duchy's official ruler by popular demand, Ferdinand joined his family in Mexico and died in Mexico City in 1841.