Sibylla of Anjou (c. 1112–1165) was a countess consort of Flanders as the wife of Count Thierry. She ruled the County of Flanders as regent during the absence of her spouse from 1147 to 1149.
In 1134, Sibylla married Thierry, Count of Flanders.[5] During his absence on the Second Crusade the pregnant Sibylla acted as regent of the county.[6]Baldwin IV, Count of Hainaut took the opportunity to attack Flanders,[6] but Sibylla led a counter-attack and pillaged Hainaut. In response Baldwin ravaged Artois. The archbishop of Reims intervened and a truce was signed, but Thierry took vengeance on Baldwin when he returned in 1149.
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Gilbert of Mons (2005). Chronicle of Hainaut. Translated by Napran, Laura. The Boydell Press.
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N. Huyghebaert, Une comtesse de Flandre à Béthanie, in "Les cahiers de Saint -André", 1964, n°2, 15p.
Runciman, Steven (1952). A History of the Crusades. Vol. II: The Kingdom of Jerusalem. Cambridge University Press.
Stroll, Mary (2004). Calixtus the Second, 1119-1124. Brill.166-167