The family name Montmorency derived from their castle in the pays de France, recorded in Latin as Mons Maurentiacus, in 993.

Maurentiacus, the name of the area surrounding the castle, meant "estate of Maurentius", probably a Gallo-Roman landowner.

During the reign of Louis VIII he distinguished himself chiefly in the south of France (Niort, La Rochelle, Bordeaux).

On the accession of Louis IX, he was one of the chief supports of the queen-regent Blanche of Castile, and was successful in reducing all vassals to obedience.

[1] His eldest son, François de Montmorency (1530–1579), was married to Diane, natural daughter of Henry II.

In 1625 he defeated the French Protestant fleet under Soubise, and seized the islands of Ré and Oleron, but the jealousy of Richelieu deprived him of the means of following up these advantages.

In 1628-1629 he was allowed to command against the Duke of Rohan in Languedoc; in 1630 he defeated the Piedmontese, and captured Carlo Doria, at Avigliana, and took Saluzzo.

In 1632 he joined the party of Gaston, duke of Orleans, and placed himself at the head of the rebel army, which was defeated by Marshal Henri de Schomberg at Castelnaudary (September 1, 1632); severely wounded, he fell into the enemy's hands and, abandoned by Gaston, was executed as a traitor at Toulouse on October 30.