Born in 1633 at Lussac-Les-Châteaux into the illustrious de Rochechouart de Mortemart family, Gabrielle was the older sister of the famous Madame de Montespan and just like her little sister, Gabrielle was celebrated for her great beauty, sharp mind and wit.
Gabrielle was the first-born child of Gabriel de Rochechouart de Mortemart and his wife Diane de Grandseigne. Her childhood was not too different from that of most noble children and Diane made sure all of her children grew up with maternal love and in a pious spirit. Since both parents had positions at court, Diane being lady-in-waiting to Anne d’Autriche and Gabriel first gentleman of the royal bedchamber, Gabrielle did not see too much of them and was left in care of nurses. Gabrielle’s education was trusted into the hands of the Dames de Saintes, there she learned all that was deemed necessary and was joined by her younger sister Françoise, which later went by the name Athénaïs. Freshly out of convent, she joined court in 1651, as the Fronde still raged on, and was placed by her parents into the household of the young Louis XIV. She did not remain in the King’s household for too long and joined that of his brother, back then called Petit Monsieur. During this time a strong friendship developed between Gabrielle and Philippe, which lasted all their lives.
In 1655, aged twenty-two, Gabrielle was married to Claude Leonor Damas de Thianges, Marquis de Thianges. The new Marquise de Thianges was not too happy with the match. Being of a house older than the Bourbons, a famed house, she thought she deserved a more high-ranking husband. Compared to her younger sister, Gabrielle discovered her gift for words earlier and was also praised for her esprit de Mortemart, something her father was famous for. It was a way to say certain things in a sometimes slightly cheeky way, but so nicely and charmingly phrased, that the victim felt flattered or amused by it. Louis XIV was not safe from it either, for the bold-tongued Gabrielle loved to tease him with how much older her house was compared to his own.
Although Gabrielle was not entirely happy with her hubby’s rank, marriage came with many freedoms that made up for it. Now she was able to freely participate in the amusements of the court, balls, visit salons, and independent from her parents. This “master-piece of nature” as Madame de Sévigné called her, became one of the great ladies of court and known to be quite haughty. Gabrielle was quite obsessed with rank and the status of her family, thinking due to how very old her family was, she was entitled to more than what was given to her.
Gabrielle also rose to very friendly terms with Louis XIV. It is a little unclear how far the friendliness went, but she was at least rumoured to share his bed from time to time. Although she captivated him with her beauty, it was her little sister who became his official mistress a few years later. Athénaïs and Gabrielle were rather close to each other and whenever possible, Gabrielle tried her very best to better their situations and ask for favours. She supported Athénaïs however she could and it was even rumoured when Athénaïs was pregnant, Gabrielle took her position briefly to keep the King entertained. Athénaïs certainly had no scruples in that department and was known to place her own creatures -maids, friends, relatives- in the King’s bed when she was not able to place herself in it due to illness or pregnancy.
The Marquise de Thianges became the mother of four children herself. Claude-Henri, born in 1663, Diane-Gabrielle, Louise-Elvide and Gabrielle. Her youngest daughter Gabrielle remained unmarried. Louise-Elvide, for which the Marquise apparently only cared little, married the, at this time sixty year old, Duc de Sforza. Her favourite daughter was clearly Diane-Gabrielle and thanks to her mother and aunt, Diane-Gabrielle made the best match. She married the Duc de Nevers, nephew of Cardinal Mazarin, and her marriage became quite a happy one.
In 1674, the Marquise left her husband behind and went for the 17th century version of a divorce, the separation of bed and board. The couple had lived apart for many years already. Upon the separation, Gabrielle’s dowry was returned to her and she set up a own household with own livrees for her servants. Her husband did not appear troubled by it.
Gabrielle was well-known at court for hosting quite wild parties as well as her spontaneous nature. She dedicated much of her life to support her siblings, especially as Madame de Montespan’s favour began to vanish. She attempted her very best to help her sister regain the lost favour and as if did not work out, both decided to at least keep it in the family again. Gabrielle apparently suggested herself that her daughter Diane-Gabrielle should be the next mistress of Louis XIV. What they did not expect, was that Louis had not much interest in Diane-Gabrielle, although she was stunning, and even more surprisingly Diane-Gabrielle herself had no interest in Louis either. She was madly in love with her poet-husband.
At the time Athénaïs fell completely out of favour, everyone expected Gabrielle would follow her and leave court. The Marquise de Thianges remained however. She had established herself as a person of influence and also kept her large apartment at Versailles. Smart as she was, she also managed to become friends with the one who had replaced her sister, the very pious Madame de Maintenon. The latter admired Gabrielle for her own piousness, then although she lived a wild live, she always had remained rather god-fearing. Unfortunately for Gabrielle, her wild lifestyle had taken a toll on her. Her beauty faded and by the age of fifty, she had to be carried pretty much everywhere by her servants.
Gabrielle de Rochechouart de Mortemart died in Paris on September 12 in 1693 and was buried at the église des religieux pénitents de Picpus, near the tomb of her father. Through her daughter Diane-Gabrielle, she became the great-grandmother of the diplomat and French Ambassador to Rome Louis-Jules Barbon Mancini-Mazarin. Gabrielle is also an ancestor of the present Prince de Monaco.