Empress Wang Zhengjun (71 BCE – CE 13), official imperial title Empress Xiaoyuan, later and more commonly known as Grand Empress Dowager Wang, born in Yuancheng (modern Handan, Hebei), is an empress during the Western Han Dynasty of China, who plays important roles during the reigns of five successive Han emperors—her husband, her son, her two stepgrandsons, and her stepgreat-grandnephew—and later (according to traditional historians, unwittingly) leads to the usurpation of the throne by her nephew Wang Mang.

She is largely viewed sympathetically by historians as an unassuming and benevolent if overly doting woman who suffered much in her long life, who tried to influence the empire as well as she could, and who was not a party to her nephew's machinations, but whose failure, leading to the downfall of the Western Han Dynasty, was her overdependence on her clan (the Wangs).