Mary, Princess Royal and Princess of Orange (d. 1660)
Mary, Princess Royal (Mary Henrietta Stuart; 4 November 1631 – 24 December 1660), was an English princess, member of the House of Stuart, and by marriage Princess of Orange and Countess of Nassau; she also acted as regent for her minor son from 1651 to 1660. She also was the first holder of the title Princess Royal.

The eldest daughter of King Charles I of England and Queen Henrietta Maria, Mary was married to the future stadtholder of the Netherlands, William II of Orange, at 9 years old in 1641. Initially, she remained in England with her parents because of the heated political situation in England until early 1642, when she and her mother left for the Netherlands. Five years later in 1647, Mary's husband inherited the titles of Prince of Orange and Stadtholder of Holland, Zeeland, Utrecht, Guelders, Overijssel and Groningen in the United Provinces of the Netherlands.

Eight days after her husband's death in 1650, Mary gave birth to a son, William III of Orange, who later became King of England, Scotland and Ireland. Mary, who became the only guardian of her son, was not popular in the Netherlands because of her support of her brothers and her difficult relationship with her mother-in-law Amalia of Solms-Braunfels, who considered the princess young and inexperienced. After the restoration of the monarchy in England in 1660, Mary departed for celebrations in London, where she fell ill with smallpox and died.