Marie of Avesnes was a noblewoman born around 1250 in the County of Hainaut, which is now part of modern-day Belgium. She was the daughter of Baldwin of Avesnes and Adelaide of Holland. Marie became the Countess of Hainaut and Holland through her marriage to William II of Holland in 1265, strengthening the ties between these regions. Marie played a significant role in the political landscape of her time, particularly during the conflicts between the House of Avesnes and the House of Dampierre. She was known for her diplomatic skills and efforts to maintain peace and stability in her territories until her death in 1285.