Mathieu de Montomorency was born in Paris, France on July 10, 1767. He was the son of Mathieu Paul Louis de Montmorency, vicomte de Laval (1748–1809) and Catherine Jeanne Tavernier de Boullongne (d. 1838). Montmorency's father was a scion of one of the oldest noble families in France, while his wife was the daughter of an aristocratic French planter in Guadeloupe. His mother's illegitimate mulatto half-brother was the famous Chevalier de Saint-Georges. He was a very tall, blonde, well-built man who had a contagious, youthful aura. Montmorency went on to seek higher education at College du Plessis, where he developed his love for the subject of philosophy and the idea of enlightenment.Montmorency was elected into the National Assembly at the very young age of 23. At the time, he was the youngest member to serve on the Constituent Assembly. Montmorency worked very diligently to make a name for himself among the other prominent members. He had great ease when it came to presenting his speeches. Although born into nobility, he did not let his arrogant reputation get the best of him. He always regarded others with great manners. His hard work in the National Assembly ultimately led him to be appointed as the secretary of the assembly.
In 1780, his father, a colonel of the Auvergne regiment, was appointed a premier gentilhomme de la chambre to King Louis XVI of France's younger brother, the Comte de Provence. However, when Catherine was denied the corresponding rank of dame pour accompagner to the prince's wife, Marie-Joséphine, due to her relatively low birth, Laval resigned his post in Provence's household. Montmorency was a very intelligent man. He was a diplomatist and a great writer. He eventually went to become a tutor for Henry, duke de Bordeaux, the grandson of Charles X.
Mathieu de Montmorency was married to his first cousin Hortense de Luynes. At the time this was seen as normal, because many noble families wanted to keep their bloodlines within each other. However, despite being married he actually paid very little attention to his wife. Due to the very relaxed nature of marriages, he often was seen without his wife. In actuality, Montmorency was madly in love with another cousin by the name of Marquise de Laval. Laval died suddenly, and Montmorency went to a great depression.
Madame de Stael ultimately brought Montmorency out of his depression. Mathieu became Mme Stael’s friend in 1790 while he was in the constituent assembly. She was 24 years old when they met, while he was only 23. Mme Stael was a very educated woman. Their friendship started after writing a series of letters to each other. His attraction towards her grew more and more through each letter.
Originally known by the title of Comte de Montmorency-Laval, Mathieu served as an adolescent with his father in the American Revolution. At the opening of the French Revolution, he joined the Third Estate and sat on the left side of the National Assembly, shifting from originally being on the Second Estate, the nobility. He served in the American War of Independence with Lafayette. America was a new nation that had built its nation on democracy and liberty. Montmorency is credited for bringing these new governmental ideas to France. Montmorency was a member of the noble class. The nobility had a very negative reputation, as they were known for being greedy and discourteous. However, Montmorency’s actions began to change the way the nobility was viewed at the start of the revolution. He was extremely generous and showed great remorse to people, unlike others. His ultimate goal was to make the French people happy, while still preserving the nobility. Years later, Montmorency went to become the Captain of the guards of the Count d’Artois. He also became the governor of the city and castle of Gompiègne and was elected the deputy of the estates general for the nobility of Montfort. These are all great accomplishments that Montmorency achieved throughout his life.
At the beginning of the Bourbon Restoration, he was promoted to the rank of maréchal de camp, and accompanied Louis XVIII to Ghent during the Hundred Days. After the Battle of Waterloo and the final defeat of Napoleon in 1815, he was made a peer of France and received the title of Vicomte de Montmorency-Laval. He was instrumental in convincing Armand-Emmanuel du Plessis, Duc de Richelieu to replace his former friend and former Bonapartist Charles Maurice de Talleyrand-Périgord as the new Prime Minister of France.
Known for strong reactionary, ultramontane, and Ultra-royalist views, Felicite became the French minister of foreign affairs under Jean-Baptiste Guillaume Joseph, comte de Villèle in December 1821. He recommended armed intervention in Spain, to restore Ferdinand VII, at the Congress of Verona in October 1822. However, he resigned his post in December, being compensated by the title of Duc de Montmorency-Laval and the cross of the Legion of Honour soon after.
He was elected to the Académie française in 1825, with few qualifications for the honour. The following year, he was named tutor to the six-year-old heir to the throne, the Duc de Bordeaux. He died two months after receiving this prestigious appointment, on 24 March 1826. He was discovered seated lifeless at the end of the Good Friday Liturgy in St. Thomas d'Aquin church in the fashionable St. Germain des Près faubourg.