King Seongjong of Joseon, previously known as Grand Prince Jalsan (Hanja: 成宗王 [乽山大君]; Born: August 19th 1457 – Died: January 20th 1494; Reigned: December 31st 1469 - January 20th 1494), born Yi Hyeol (이혈/李娎) was the ninth king of the Joseon Dynasty of Korea. He succeeded his uncle, King Yejong in 1469 and ruled until 1494.
He was grandson of King Sejo, nephew of King Yejong. He succeeded King Yejong in 1469 when the weak king died and his son was too young to succeed him. Since he was too young to govern the kingdom effectively (he was 13 when he was crowned), Queen Jeonghui of Papyeong Yoon Clan, his grandmother, ruled the nation in his name, along with the king's mother, Queen Dowager In-soo a.k.a Queen Sohye of Cheongju Han Clan (whose husband - Crown Prince Uigyeong Yi Jang had never actually been king, but he was ascended to throne posthumously). In 1476, at the age of 20, he began to govern the country in his own name.
His reign was marked by the prosperity and growth of the national economy, based on the laws laid down by kings Taejong, Sejong, and Sejo. He himself was a gifted ruler. In 1474, the code of law, first ordered by King Sejo, was completed and put into effect. Seongjong also ordered revisions and improvements to the code.
Besides the law, he also encouraged Confucian scholars; He greatly expanded Hongmungwan (홍문관, 弘文館), the royal library and advisory council to the king at the same time, and strengthened so-called Three Offices (Hongmungwan, Office of Inspector General, Office of Censors) as check and balance on the Royal Court. For the first time since King Sejong, he brought many liberal Confucian scholars to his court, whose political views went against those of the conservative officials (members of the nobility) who had helped kings Taejong and Sejo to power. In this way he made his rule more effective by appointing able administrators regardless of their political views. His policy resulted in many positive innovations, increasing his number of supporters. The king himself was an artist and scholar, and liked to argue about the finer points of politics with more liberal scholars. He encouraged scholars to publish numerous books about geography and social etiquette, for example, as well as areas of knowledge that benefited the common people.
He also sent several military campaigns against the Jurchens on the northern border in 1491, like many of his predecessors. The campaign, led by Gen. Heo Jong (허종/許琮), was successful, and the defeated Jurchens led by Udige (兀狄哈) retreated to the north of Amrok River. King Seongjong was succeeded by his son, King Yeonsan the Terrible, in 1494.