Archduke Ferdinand Karl of Austria-Este (1 June 1754 – 24 December 1806) was a son of Holy Roman Emperor Franz I and Maria Theresa of Austria. He was the founder of the House of Austria-Este and Governor of the Duchy of Milan between 1765 and 1796. He was also designated as the heir to the Duchy of Modena and Reggio, but he never reigned, owing to the Napoleonic Wars.

Ferdinand was born at the Schönbrunn Palace in Vienna as the fourth son and fourteenth child of the Holy Roman Emperor Franz I and of his wife, Maria Theresa of Austria.

In 1763, the last Este Duke of Modena, Ercole III (who did not die until 1803), signed a treaty with the Empress Maria Theresa engaging the nine-year-old Ferdinand to his only daughter Maria Beatrice, making him thus his heir. There had been an earlier treaty in 1753 making Ferdinand's older brother Peter Leopold the heir to the Duchy of Modena, but in 1761, Peter Leopold became heir to the Grand Duchy of Tuscany, which required a change to the Modena agreement.

In 1771, the Perpetual Imperial Diet approved the eventual investiture of Ferdinand with the imperial fiefs held by Ercole III.

On 15 October 1771, Ferdinand married Maria Beatrice Ricciarda d'Este (7 April 1750-14 Nov 1829), only surviving child of Duke Ercole III of Modena and Reggio (although the marriage was not a requirement of Ferdinand's eventual succession). Festivities arranged for this occasion included the operas Ascanio in Alba by Mozart and Il Ruggiero by Johann Adolph Hasse.

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