Duke of Montmorency was a title of French nobility that was created several times for members of the Montmorency family, who were lords of Montmorency, near Paris.

François de Montmorency, 2nd Duke of Montmorency was a French noble, governor, diplomat and soldier during the latter Italian Wars and the early French Wars of Religion. The son of Anne de Montmorency, favourite of the king and Madeleine of Savoy, Montmorency began his political career during the coronation of Henri II in 1547. With the resumption of the Italian Wars in 1551 he fought at the capture of Chieri, the famous defence of Metz and the defence of Thérouanne. In the latter engagement he was captured by Imperial forces, and put up for ransom. He would spend the next three years in captivity before returning to France in 1556. Returning to the conflict immediately he participated in the disastrous Saint-Quentin campaign in which the French army was destroyed and his father captured. After serving as a lieutenant in Picardie he found himself gaining advantage on the death of Henri II, the new Guise regime compensating the Montmorency family for their seizure of the grand maître title with the provision of a Marshal baton to Montmorency.