Deposed Queen Yoon was sentenced to death by her husband, King Seongjong, on account of extreme jealousy and inappropriate behaviors. It remains unclear whether her unusual behavior resulted from a psychiatric disorder. In this study, we addressed the issue of whether deposed Queen Yoon suffered from bipolar disorder. We reviewed Seongjong Sillok (Veritable Records of King Seongjong), Joseon Wangjo Sillok (Veritable Records of the Joseon Dynasty), and the available literature on deposed Queen Yoon. A review of the literature showed that deposed Queen Yoon might have experienced depressive and manic episodes. Her symptoms of episodic course, familial tendency of mood symptoms, and postpartum onset suggest that she might have suffered from bipolar disorder. Her symptoms and clinical course suggest that deposed Queen Yoon might have suffered from bipolar disorder. To the best of our knowledge, this is the first report suggesting that deposed Queen Yoon might have suffered from bipolar disorder.