Individual Details

Marriage

On 27 May 1234 at the age of thirteen, Margaret became the queen consort of France and wife of Louis IX of France, by whom she had eleven children. She was crowned on the following day.
Margaret, like her sisters, was noted for her beauty, she was said to be "pretty with dark hair and fine eyes",[4] and in the early years of their marriage she and Louis enjoyed a warm relationship. Her Franciscan confessor, William de St. Pathus, related that on cold nights Margaret would place a robe around Louis' shoulders, when her deeply religious husband rose to pray. Another anecdote recorded by St. Pathus related that Margaret felt that Louis' plain clothing was unbecoming to his royal dignity, to which Louis replied that he would dress as she wished, if she dressed as he wished.

During the Seventh Crusade
Margaret accompanied Louis on his first crusade and was responsible for negotiations and ransom when he was captured. She was thus for a brief time the only woman ever to lead a crusade. During this period, while in Damietta, she gave birth to her son Jean Tristan.
The chronicler Joinville, who was not a priest, reports incidents demonstrating Margaret's bravery after Louis was made prisoner in Egypt: she decisively acted to assure a food supply for the Christians in Damietta, and went so far as to ask the knight who guarded her bedchamber to kill her and her newborn son if the city should fall to the Arabs. Joinville also recounts incidents that demonstrate Margaret's good humor, as on one occasion when Joinville sent her some fine cloth and, when the queen saw his messenger arrive carrying them, she mistakenly knelt down thinking that he was bringing her holy relics. When she realized her mistake, she burst into laughter and ordered the messenger, "Tell your master evil days await him, for he has made me kneel to his camelines!"
However, Joinville also remarked with noticeable disapproval that Louis rarely asked after his wife and children. In a moment of extreme danger during a terrible storm on the sea voyage back to France from the Crusade, Margaret begged Joinville to do something to help; he told her to pray for deliverance, and to vow that when they reached France she would go on a pilgrimage and offer a golden ship with images of the king, herself and her children in thanks for their escape from the storm. Margaret could only reply that she dared not make such a vow without the king's permission, because when he discovered that she had done so, he would never let her make the pilgrimage. In the end, Joinville promised her that if she made the vow he would make the pilgrimage for her, and when they reached France he did so.

Political significance
The Treaty of Paris came about since the relationship between Louis and Henry III of England had improved, since both they and their younger brothers had married the four sisters from Provence. Margaret was present during the negotiations, along with all her sisters and her mother.
In later years Louis became vexed with Margaret's ambition. It seems that when it came to politics or diplomacy she was indeed ambitious, but somewhat inept. An English envoy at Paris in the 1250s reported to England, evidently in some disgust, that "the queen of France is tedious in word and deed," and it is clear from the envoy's report of his conversation with the queen that she was trying to create an opportunity for herself to engage in affairs of state even though the envoy was not impressed with her efforts. After the death of her eldest son Louis in 1260, Margaret induced the next son, Philip, to swear an oath that no matter at what age he succeeded to the throne, he would remain under her tutelage until the age of thirty. When Louis found out about the oath, he immediately asked the pope to excuse Philip from the vow on the grounds that he himself had not authorized it, and the pope immediately obliged, ending Margaret's attempt to make herself a second Blanche of Castile. Margaret subsequently failed as well to influence her nephew Edward I of England to avoid a marriage project for one of his daughters that would promote the interests in her native Provence of her brother-in-law, Charles of Anjou, who had married her youngest sister Beatrice.

Death

After the death of Louis on his second crusade, during which she remained in France, she returned to Provence. She was devoted to her sister Queen Eleanor of England, and they stayed in contact until Eleanor's death in 1291. Margaret herself died four and a half years after her sister, on 21 December 1295, at the age of seventy-four. She was buried near (but not beside) her husband in the Basilica of St-Denis outside Paris. Her grave, beneath the altar steps, was never marked by a monument, so its location was unknown; probably for this reason, it was the only royal grave in the basilica that was not ransacked during the French Revolution, and it probably remains intact today.
Margaret outlived eight of her eleven children; only Blanche, Agnes and Robert outlived their mother.