The title of Duke of Montmorency was created several times for members of the Montmorency family, who were lords of Montmorency, near Paris.
The first creation was in 1551 for Anne of Montmorency, Constable of France. This title was forfeited by the fourth Duke, who was executed for treason in 1632.
The duchy was then recreated in 1633 for his sister Charlotte Marguerite of Montmorency and her husband the Prince of Condé. This title was renamed Duke of Enghien in 1689.
The original Duke of Montmorency title was transferred to the duchy of Beaufort, which had been conferred on Charles François Frederic of Montmorency-Luxembourg, Prince de Tingry, in 1688. This latter title was authorised to pass through the female line to the branch of Montmorency-Fosseux in 1767 and became extinct in 1862.
However, in 1864 the Emperor Napoleon III extended the title of Duke of Montmorency to the Duke of Valençay, second son of the Duke of Talleyrand by his wife Anne Louise Charlotte of Montmorency, who was a sister of the 6th Duke of Montmorency. His male issue became extinct in 1951, when the Dukedom of Montmorency again became extinct.
The title was forfeited by the last duke upon execution, and returned to the royal domain.
The title of Duke of Montmorency was changed to Duke of Enghien in 1689.
On the death of the last duke in 1830, the title passed to Louis Philippe III, Duke of Orléans, a great-great-grandson of the Louis I, Duke of Enghien through the female line. He had become King of the French as Louis Philippe I a month earlier.
The title of Duke of Beaufort was changed to Duke of Montmorency in 1689.
On the death of the last duke in 1951, the title became extinct.