Charles II François Frédéric de Montmorency (December 31, 1702 – May 18, 1764), was a French aristocrat who held a number of titles, including 8th Duke of Piney-Luxembourg, 2nd Duke of Montmorency, Prince of Aigremont and of Tingry, Count of Bouteville, of Lassé, of Dangu and of Luxe.

His father also succeeded his grandfather, Marshal François-Henri de Montmorency, as Duke of Piney-Luxembourg in 1695.

[2] He gave refuge to Jean-Jacques Rousseau, the famous French philosopher, at the "Small Castle" at Montmorency during 1759 to 1762 (an area which was owned by Charles Le Brun and Pierre Crozat; was distinguished from another stay of Rousseau in Montmorency: Mont-Louis, previously offered by Mr. Mathas, tax attorney for the Prince of Condé)[3] when he was quarreling with Madame d'Epinay, his protectress.

Before her death at Rue Neuve-des-Petits-Champs in Paris on 29 October 1747, they had two children:[6] In 1750, he married Madeleine Angélique Neufville de Villeroy, the wealthy widow of Joseph Marie de Boufflers, Duke of Boufflers.

The daughter of Louis Nicolas de Neufville, 3rd Duke of Villeroy, and Marguerite Le Tellier, she served as a Dame du Palais to Queen Marie Leszczyńska at Versailles between 1734 and 1749.