Honoré III ruled as Prince of Monaco and was Duke of Valentinois for almost sixty years from 1733 to 1793. Honoré was the son of Jacques I, Prince of Monaco and his wife, Louise Hippolyte, Princess of Monaco.
On 20 May 1732, he moved to Hôtel Matignon in Paris with his father and remained there, even after the proclamation in 1733 of him as Prince of Monaco. Antoine Grimaldi, le Chevalier de Grimaldi, acted as regent for the prince between 1732 and 1784, when Honoré chose to reside in Paris. This situation remained the same for half a century until Antoine's death in 1784, when Honoré III was already 64 years old. Although he was open to the revolutionary ideas of the time, he was imprisoned on 20 September 1793. At his liberation a year later, he was ruined, and his property under seal.
In 1751, he married Maria Caterina Brignole. The couple had two children; Honoré IV, Prince of Monaco and Joseph Grimaldi before divorcing in 1770, and Marie-Catherine married the Prince de Condé in 1798.