Mary, Countess of Blois, also known as Marie of Avesnes, (1200–1241) was countess of Blois from 1230 to 1241.

She was the daughter of Walter of Avesnes and Margaret of Blois.

[1] In 1226, Mary married Hugh I of Châtillon, a count from Châtillon-sur-Marne, son of Gaucher III of Châtillon and Elisabeth of Saint-Pol.

[2] They had five children: Her eldest son, John, succeeded her in Blois.

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