Yeonsan-gun or Prince Yeonsan, born Yi Yung or Lee Yoong, was the 10th king of Korea's Joseon Dynasty. He was the eldest son of Seongjong by his second wife, Lady Yoon. He is often considered the worst tyrant of the Joseon Dynasty, and perhaps all of Korean history, notorious for launching two bloody purges of the seonbi scholar elite. He also seized a thousand women from the provinces to serve as palace entertainers, and appropriated the Seonggyungwan study hall as a personal pleasure ground. Overthrown, Yeonsan-gun did not receive a temple name.