Jeongjong (Korean: 정종; Hanja: 定宗; 923 – 13 April 949), personal name Wang Yo, was the third king of the Goryeo dynasty of Korea.
Jeongjong rose to the throne after his half-brother King Hyejong died, and set to reducing the power of various royal in-laws, including Wang Gyu and Pak Sul-hui.
[1] However, Jeongjong was not successful in his attempts due to opposition from the nobility based in Gaegyeong.
[2] Jeongjong became paranoid however that people inside the palace were conspiring to kill him and he then started to go insane.
After four years of his reign, he died just after he signed a royal decree to make his brother, the fourth prince Wang So (known as Gwangjong), king instead of his son.