Countess Joan of Rethel was a noblewoman from the 12th century, known for her marriage to Hugh II of Rethel. She played a significant role in the political landscape of her time, as her family was influential in the region of Champagne in modern-day France. Joan was the daughter of Baldwin IV of Jerusalem and Melisende of Jerusalem, linking her to the royal lineage of the Crusader States. Her marriage helped strengthen alliances between noble families, which was crucial during the turbulent times of the Crusades.