Jeongjong (31 August 1018 – 24 June 1046), personal name Wang Hyŏng, was the 10th king of Korea's Goryeo dynasty. He was the second son of King Hyeonjong, and the younger brother of King Deokjong. At the age of four in 1022, he was made Naesaryeong, a position of high rank, and designated the Prince of Pyongyang. Jeongjong was greatly concerned with national defense, and began constructing fortresses along the northern border in the first year of his reign. In 1037, Goryeo was invaded by the Liao dynasty. In 1044, the Cheolli Jangseong was completed, an enormous wall across northern Korea. Jeongjong also concerned himself with the material support of the army, distributing state land to indigent soldiers in 1036. Just before his death in 1046, Jeongjong established primogeniture as national law.

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