One of the conditions of the Treaty of Paris, signed on 12 April 1229, stipulated that Joan was to be married to Alphonse, Count of Poitiers and brother of King Louis IX of France, and a Papal dispensation for their 4th degree of consanguinity is dated on 26 June of that year.
She was thereby not a part of the Occitanian culture, felt no sympathy for the Albigensians and did nothing to prevent the hunt of them issued by the Inquisition.
The couple took control over their lands in October 1250, and made their official entrance as Countess and Count of Toulouse in May 1251.
Joan was the only surviving child and heiress of Raymond VII, Count of Toulouse, Duke of Narbonne, and Marquis of Provence, so under Provençal and French law, the lands should have gone to her nearest male relative; however, in this case the closest relative was a female, Philippa de Lomagne (daughter of Marie d'Anduze, in turn eldest daughter of Pierre Bermond VI d'Anduze, eldest son of Constance of Toulouse, eldest half-sister of Raymond VII).
[5] One specific bequest in Alphonse's will, giving his wife's lands in the Comtat Venaissin to the Holy See, was allowed, and it became a Papal territory, a status that it retained until 1791.