Marie of Brienne (c. 1224–1275) was Latin Empress as the wife of Baldwin II of Courtenay. She served as regent during the absence of Baldwin II twice: in 1237–1239, and in 1243–1257.
Family
She was a daughter of John of Brienne and his third wife Berenguela of Leon. Marie was a younger, paternal half-sister of Yolande of Jerusalem. She was also a sister of Alphonso of Brienne.
Marriage
On 19 April 1229, Marie was betrothed to Baldwin II, junior co-ruler of her father as Emperor of the Latin Empire. The marriage was intended to establish a dynastic alliance between the two co-rulers. Marie was at most five years old at the time of her betrothal, her parents having married in 1224.
Their marriage took place in 1234. The bride was about ten years old, the groom seventeen. Their marriage was recorded in the chronicle of Alberic of Trois-Fontaines. By her marriage, Marie became the junior co-empress of the Latin Empire, the senior one being her mother.
Empress
In 1235-36, Constantinople was besieged by the combined forces of Ivan Asen II of Bulgaria and John III Doukas Vatatzes of the Empire of Nicaea. The city was defended by only its small garrison of knights, the fleet of the Republic of Venice and a minor force sent by Geoffrey II of Villehardouin, Prince of Achaea to reinforce the defense. The city was only spared conquest because of a quarrel between the two allies over who would receive command of the city in the event of a success. John V. A. Fine has suggested that Ivan Asen realised the greater threat posed to the Second Bulgarian Empire by the expansion of Nicaea rather than the weakened Latin Empire.
In any case, John of Brienne had taken command of the defense of Constantinople. Baldwin II undertook another mission, heading to Western Europe in attempt of raising the funds and recruiting the armed forces needed to secure the survival of their Empire. John died on 27 March 1237, Berenguela following him on 12 April. The twelve-year-old Marie was left in nominal command of the city, as the sole representative of the imperial family present in it. Baldwin would not return until July 1239.
Baldwin returned at the head of a Crusading force from Western Europe, variously estimated to include as few as thirty thousand men or as many as sixty thousand. This force was joined by a contingent of Cumans, combining to besiege Tzurulum, a Nicaean stronghold in Thrace. The city fell in 1240 but this seems to have been the only success of this force. They are not mentioned afterwards. John V. A. Fine presumes that most of them returned to their homes in Western Europe, only a few of them joining the existing garrison of Constantinople. For the moment, the Latin Empire had ensured its continued survival. Marie was approximately fifteen-year-old at the time her husband returned to his capital.
On 15 April 1240 (Easter), Baldwin II was crowned emperor in Hagia Sophia. Their only known son, Philip of Courtenay, was born in 1243. However this period of relative peace for the couple was not to last. Baldwin left for the Kingdom in France by the end of 1243, intending to seek support from Louis IX of France. In his absence Marie became regent of the Empire, with Philip of Toucy as her initial co-regent. Philip was a son of Narjot of Toucy and his first wife. His mother was a daughter of Theodore Branas and Agnes of France. Baldwin was absent for several years, first staying in France and then joining Louis IX in the Seventh Crusade. He returned by 8 October 1248, the date of a charter that empowered her to mortgage his western lands in order to pay the huge debt of 24,000 hyperpers.