Francis Hyacinth (Italian: Francesco Giacinto; 14 September 1632 – 4 October 1638) was Duke of Savoy and ruler of the Savoyard states under the regency of his mother Christine Marie.

Born at the Castle of Valentino in Turin he was the eldest surviving son of Victor Amadeus I, Duke of Savoy and his wife Christine Marie of France.

While Duke of Savoy he also held the subsidiary titles of Marquess of Saluzzo, count of Aosta, Moriana and Nice, and claimant King of Jerusalem.

Having succeeded his father at such a young age, Francis Hyacinth did not rule de facto being only 5 years old.

Having caught a fever, he died at the Castle of Valentino, and was succeeded by his brother Charles Emmanuel II.