Sejong the Great

Sejong (Korean: 세종; Hanja: 世宗; 15 May 1397 – 8 April 1450), personal name Yi To (이도; 李祹), commonly known as Sejong the Great (세종대왕; 世宗大王), was the fourth monarch of the Joseon dynasty of Korea. He is regarded as one of the greatest rulers in Korean history, and is remembered as the inventor of Hangul, the native alphabet of the Korean language.
Initially titled Grand Prince Chungnyeong (충녕대군; 忠寧大君), he was the third son of King Taejong and Queen Wongyeong. In 1418, Sejong replaced his eldest brother, Yi Che, as crown prince; a few months later, Taejong voluntarily abdicated the throne in Sejong's favor. In the early years of Sejong's reign, King Emeritus Taejong retained vast powers, most notably absolute executive and military power, and continued to govern until his death in 1422.
Sejong reinforced Korean Confucian and neo-Confucian policies, and enacted major legal amendments (공법; 貢法). He personally created and promulgated the Korean alphabet, encouraged advancements in science and technology, and introduced measures to stimulate economic growth. He launched military campaigns to the north and implemented a relocation policy (사민정책; 徙民政策), establishing settlements in the newly conquered areas. He also ordered the military campaign against Tsushima island of 1419.
From 1439, he became increasingly ill and his eldest son, Crown Prince Yi Hyang, acted as regent. Sejong died on 8 April 1450.
Sejong was born Yi To (이도; 李祹) on 15 May 1397, in Junsubang, Hanseong (Seoul), Joseon to Yi Pang-wŏn and a lady of the influential Yeoheung Min clan (later Queen Wongyeong). While records of Yi's childhood are scarce, it is known that Yi was born outside Gyeongbokgung when his father, Yi Pang-wŏn, was not yet heir to the throne.
In 1408, Yi's father arranged his marriage to Lady Sim of the Cheongsong Sim clan [ko], who would later become Queen Soheon. In 1412, Yi To was granted the title Grand Prince Chungnyeong (충녕대군; 忠寧大君). In 1414, he had his first son, who would later become Munjong.
As Taejong's eldest son, Grand Prince Yangnyeong was to inherit the throne. However, Taejong, as well as court officials, increasingly deemed Yangnyeong unsuitable for the role due to his erratic and irresponsible behavior. In a series of escalating events involving Yangnyeong's affair with Eori, a concubine of Kwak Sŏn, Yangnyeong was ultimately deposed as crown prince.
In mid-1418, court officials petitioned Taejong to consider a new candidate for the throne. Following primogeniture, Taejong initially considered Yangnyeong's eldest son for the role. However, the officials objected and insisted that Taejong select a wise person as heir apparent. King Taejong asked the officials to propose an alternative. According to the Veritable Records, they gave an indirect response: "The father knows his sons best, as the king knows his subjects best." Taejong judged his second son, Grand Prince Hyoryeong, to have a disposition too soft for the role, and would be unable to drink with emissaries from Ming dynasty to entertain them. He then proposed Chungnyeong, whom he felt was intelligent and sharp in matters of politics. The officials welcomed the decision and confirmed that Chungnyeong had been their preferred choice. On 8 July 1418, Chungnyeong was made crown prince of Joseon.
On 18 September 1418, Chungnyeong ascended the throne as King Sejong, following Taejong's abdication. However, Taejong retained military power and continued to make major political decisions as king emeritus (상왕; 上王) until his death. Sejong did not challenge Taejong's authority and deferred to his father during this period. Perpetually wary of royal authority falling into the thrall of the queen's clan, Taejong had Sejong's father-in-law, Shim On, executed on charges of treason. Other members of the queen's family were exiled or made commoners, which left Queen Soheon politically isolated and unable to protest.
Despite inheriting significantly strengthened royal authority, Sejong did not suppress the press and promoted meritocracy through gwageo, the national civil service exam.
During the Goryeo period, monks wielded strong political and economic influence. However, in Joseon, Buddhism was considered a false philosophy and the monks were viewed as corrupted by power and money.
Likewise, Sejong continued Joseon's policies of "worshiping Confucianism and suppressing Buddhism" (Korean: 숭유억불; Hanja: 崇儒抑佛). He banned monks from entering Hanseong and reduced the seven schools of Buddhism down to two, Seon and Gyo, drastically decreasing the power and wealth of the religious leaders. One of the key factors in this suppression was Sejong's reform of the land system. This policy resulted in temple lands being seized and redistributed for development and monks losing large amounts of economic influence. Furthermore, he performed government ceremonies according to Confucianism and encouraged people to behave according to the teachings of Confucius.
At the same time, Sejong sought to alleviate religious tensions between Confucianism and Buddhism. The Seokbosangjeol (석보상절; 釋譜詳節), a 24-volume Korean-language biography of Buddha translated from Chinese Buddhist texts, was commissioned and published in Sejong's reign by Grand Prince Suyang, in mourning for Queen Soheon, a devout Buddhist. Sejong advocated the project—despite fierce opposition from his courtiers—and condemned the hypocrisy of those who privately worship the Buddha yet publicly rebuke others for doing so.
In 1427, Sejong issued a decree against the Huihui (Korean Muslim) community that had enjoyed special status and stipends since the Yuan dynasty's rule over Goryeo. The Huihui were forced to abandon their headgear, close down their ceremonial hall – a mosque in Gaegyeong, present-day Kaesong – and worship like everyone else. No further records of Muslims exist during the Joseon era.
In the early years of the Joseon dynasty, the economy operated on a barter system, with cloth, grain, and cotton being the most common forms of currency. In 1423, under King Sejong's administration, the government attempted to introduce a national currency modeled after the Tang dynasty's kaiyuan tongbao (開元通寶). The resulting Joseon tongbo (조선통보; 朝鮮通寶) was a bronze coin, backed by a silver standard, with 150 coins being equal to 600 grams of silver. However, production ceased in 1425 due to high manufacturing costs, as the exchange rate dropped below the coin's intrinsic value.
In 1445, Sejong consolidated the various sujoji records, previously managed by various government offices, and placed them under the administration of the Ministry of Taxation (Hojo) to improve transparency in Joseon's fiscal policies.
King Sejong was an effective military planner and created various military regulations to strengthen the safety of his kingdom. During his reign great technological advancements were made in the manufacture of gunpowder and firearms. Hand cannons, known as Wangu (완구; 碗口), first built in 1407 and 1418, were improved upon, and the Sohwapo (소화포; 小火砲), Cheoljetanhwan (철제탄환), Hwapojeon (화포전; 火砲箭) and the Hwacho (화초; 火硝) were invented during his reign.
None of these had yet reached a satisfactory level for Sejong. In the 26th year of his reign, he had the cannon foundry Hwapojujoso (화포주조소; 火砲鑄造所) built to produce a new standard cannon with outstanding performance, and in the following year, he undertook a complete overhaul of the cannon. The Chongtongdeungnok (총통등록; 銃筒謄錄) compiled and published in the 30th year his reign, was an illustrated book that described the casting methods, gunpowder usage, and specifications of the guns. The publication of this book is considered a remarkable achievement that marked a new era in the manufacture of artillery during the Joseon Dynasty.
In June 1419, under his father's counsel, Sejong ordered the third and last military campaign of Tsushima. This incident is known as the Gihae Expedition in Korean and Ōei Invasion in Japanese. The military expedition was aimed at eradicating the taproot of the Japanese pirates' pillaging the southern villages of the Joseon dynasty. During the invasion, 245 Japanese were executed or killed and another 110 were captured, while 180 Korean soldiers died. Around 150 who had been kidnapped (146 Chinese and 8 Koreans) were also freed. A truce was made in July 1419, and the Joseon army returned to the Korean Peninsula, but no official documents were signed until 1443. In this agreement, known as the Treaty of Gyehae, the daimyo of Tsushima was obliged to pay tribute to the Joseon monarch, and in return, the Sō clan was allowed to serve as a diplomatic intermediary between Korea and Japan, as well as retain exclusive trade rights.
In 1433, Sejong sent Kim Chongsŏ to the north to conquer the Jurchens. The military campaign captured several fortresses and expanded the Korean territory northward up to the Songhua River.
Sejong promoted science. In 1420, Sejong created a royal academy within Gyeongbokgung known as the Hall of Worthies. The institute was responsible for conducting scientific research with the purpose of advancing the country's technology. The Hall of Worthies was designed to host Joseon's best and brightest thinkers, with the government offering grants and scholarships to encourage young scholars to attend.
In 1428, Sejong ordered the printing of one thousand copies of a farmer's handbook. The following year, he published the Nongsa Jikseol (농사직설; 農事直說; lit. 'Straight Talk on Farming'), a compilation of various farming methods accommodative to Korea's climate and soil conditions. The book dealt with planting, harvesting, and soil treatment, and contained information about the different farming techniques that scientists gathered from different regions of Korea. These techniques were essential for maintaining the newly adopted intensive and continuous cultivation methods.
One of Sejong's close associates was the inventor Jang Yeong-sil. Jang, who was originally a government-owned nobi from Dongnae, appointed as court technician by Sejong in 1423. Jang had been released from nobi by Taejong. Sejong appointed Jang to a byeoljwa (별좌; 別坐), responsible for crafting and repairing royal items.
In 1442, Jang Yeong-sil made one of the world's first standardized rain gauges named cheugugi (측우기; 測雨器). This model has not survived, with the oldest existing Korean rain gauge being made in 1770, during the reign of King Yeongjo. According to the Daily Records of the Royal Secretariat (승정원일기; 承政院日記; Seungjeongwon Ilgi), Yeongjo wanted to revive the glorious times of Sejong the Great, and started reading chronicles from that era. When he came across the mention of a rain gauge, Yeongjo ordered a reproduction. Since there is a mark of the Qing dynasty ruler Qianlong (r. 1735–96), dated 1770, this Korean-designed rain gauge is sometimes misunderstood as having been imported from China.
In 1434, Jang Yeong-sil, tasked by King Sejong, invented the gabinja (갑인자; 甲寅字), a new type of printing press. This printing press was said to be twice as fast as the previous model and was composed of copper-zinc and lead-tin alloys.
Sejong also wanted to reform the Korean calendar system, which was at the time based upon the longitude of the Chinese capital. He had his astronomers create a calendar with the Joseon capital of Hanseong as the primary meridian. This new system allowed Joseon astronomers to accurately predict the timing of solar and lunar eclipses.
In the realm of traditional Korean medicine, two important treatises were written during his reign. These were the Hyangyak Jipseongbang (향약집성방; 鄕藥集成方) and the Euibang Yuchwi (의방유취; 醫方類聚), which historian Kim Yong-sik says represents "the Koreans' efforts to develop their own system of medical knowledge, distinct from that of China".
In 1426, Sejong enacted a law that granted government serfs (노비; 奴婢; nobi) women 100 days of maternity leave after childbirth, which, in 1430, was lengthened by one month before childbirth. In 1434, he also granted the husbands 30 days of paternity leave.
In order to provide equality and fairness in taxation for the common people, Sejong issued a royal decree to administer a nationwide public opinion poll regarding a new tax system called Gongbeop in 1430. Over the course of five months, the poll surveyed 172,806 people, of which approximately 57% responded with approval for the proposed reform.
Joseon's economy depended on the agricultural output of the farmers, so Sejong allowed them to pay more or less tax according to the fluctuations of economic prosperity and hard times. Because of this, farmers could worry less about tax quotas and instead work at maintaining and selling their crops.
It is said that once, when the palace had a significant surplus of food, the king distributed it to poor peasants who needed it. It is also said that Sejong the Great created relief programs for those affected by floods, giving them food and shelter. Otherwise the state maintained a permanent grain dole, that existed since the days of Unified Silla.
Sejong composed the famous Yongbieocheonga ("Songs of Flying Dragons"; 1445), Seokbo Sangjeol ("Episodes from the Life of Buddha"; July 1447), Worin Cheongang Jigok ("Songs of the Moon Shining on a Thousand Rivers"; July 1447), and Dongguk Jeongun ("Dictionary of Proper Sino-Korean Pronunciation"; September 1447).
One of Sejong's closest friends and mentors was the 15th century musician Bak Yeon. Together they composed over two hundred musical arrangements. Sejong's independent musical compositions include the Chongdaeop ('Great Achievements'), Potaepyeong ('Preservation of Peace'), Pongnaeui ('Phoenix'), and Yominrak ('A Joy to Share with the People'). Yominrak continues to be a standard piece played by modern traditional Korean orchestras, while Chongdaeop and Potaepyeong are played during the Jongmyo Jerye (memorials honoring the kings of Joseon).
In 1418, during Sejong's reign, scholars developed the Pyeongyeong (편경; 編磬), a lithophone modeled on the Chinese bianqing. The Pyeongyeong is a percussion instrument consisting of two rows of 8 pumice slabs hung on a decorative wooden frame with a 16-tone range and struck with an ox horn mallet. It was manufactured using pumice mined from the Gyeonggi Province and was primarily used for ceremonies.
Sejong's contribution to the arts continued long after his death; he had always wanted to use Korean music rather than Chinese music for ancestral rituals, but conservative court officials stopped his efforts. However, when Sejong's son, King Sejo, rose to the throne, he modified the ritual music composed by his father and created the 'Jongmyo court music', which was used for royal ancestral rituals and is now inscribed as an UNESCO Intangible Cultural Hertiage.
King Sejong profoundly affected Korea's history with the creation and introduction of hangul, the native phonetic writing system for the Korean language. Although it is widely assumed that he ordered the Hall of Worthies to invent the script, contemporaneous records such as the Veritable Records of King Sejong and Chŏng Inji's preface to the Hunminjeongeum Haerye emphasize that Sejong invented it himself.
Before the creation of the new alphabet, the people of Joseon primarily used Classical Chinese to write, alongside a few writing systems like idu, hyangchal, gugyeol, and gakpil – which used Chinese characters to approximate sounds of the Korean language – that had been in use since hundreds of years before hangul. However, due to the fundamental differences between the Korean and Chinese languages, and the large number of Chinese characters required, lower-class people of Joseon lacked the privilege of education and were illiterate. To promote literacy, King Sejong created hangul (which initially had 28 letters, four of which, ㆆ, ㆁ, ㅿ, and ·, are no longer in use).
Hangul was completed in 1443 and published in 1446 along with a 33-page manual titled Hunminjeongeum, explaining what the letters are as well as the philosophical theories and motives behind them.
King Sejong faced backlash from the noble class as many disapproved of the idea of a common writing system, with some openly opposing its creation. Many within the nobility believed that giving the peasants the ability to read and write would allow them to find and abuse loopholes within the law. Others felt that hangul would threaten their families' positions in court by creating a larger pool of civil servants. The Joseon elite continued to use the Chinese hanja long after Sejong's death. Hangul was often treated with contempt by those in power and received criticism in the form of nicknames, including eonmun ("vulgar script"), amkeul ("women's script"), and ahaekkeul ("children's script"). It was commonly used for areas like casual writing, prose and bookkeeping, especially by the urban middle class like administrators and bureaucrats. It notably gained popularity among women and fiction writers, with former usually often not having been able to get access to hanja education.
In 1504, the study and publication of hangul was banned by Yeonsangun. Its spread and preservation can be largely attributed to three main factors: books published for women, its use by Buddhist monks, and the introduction of Christianity in Korea in 1602. Hangul was brought into the mainstream culture in the 16th century due to a renaissance in literature and poetry. It continued to gain popularity well into the 17th century, and gained wider use after a period of nationalism in the 19th century. In 1849, it was adopted as Korea's national writing system, and saw its first use in official government documents. After the Treaty of 1910, hangul was outlawed again until the liberation of Korea in 1945.
Sejong suffered from eye diseases and deteriorating vision and likely had health issues linked to excessive meat consumption all throughout his life. Sejong's love for meat is clear from a comment by King Emeritus Taejong. When Sejong stopped eating fish and meat to mourn after the death of Jeongjong – Sejong's uncle and Taejong's older brother – Taejong remarked that Sejong had always found it hard to eat without meat since he was a child. Sejong also started having musculoskeletal pain at the age of 22. One day he was supposed to organize a farewell party for the emissaries to the Ming dynasty but was in too much pain to do so. Sejong said: "My waist and back are stiff and immobile, so it is hard to bend or straighten." There is speculation that he had diabetes, but there is inadequate evidence for a modern medical diagnosis. There is also an account of Sejong's having a disease that roughly translates to palsy (풍증; 風症) and essential tremor (수전증; 手顫症), but terminology of the 15th century Korean traditional medicine does not translate well.
Sejong died on 8 April 1450, on the Gregorian calendar, at the residence of Grand Prince Young-eung at the age of 52. He was buried at Yeongneung (영릉; 英陵) in the same mound as his wife, Queen Soheon, who had died four years earlier. His tomb is located in Yeoju, South Korea.
His successor was his first son, Yi Hyang (posthumously King Munjong). Sejong was concerned that sickly Munjong would die early and leave his vulnerable young son to reign, so he asked scholars from the Hall of Worthies to look after his young grandson, Danjong. As predicted, Munjong died two years after his ascension, and the political stability enjoyed in the past decades disintegrated when Danjong became the sixth king of Joseon at the age of 12. Eventually, Sejong's second son, Grand Prince Suyang (later known as King Sejo), usurped the throne in 1455. When six court officials were implicated in a plot to restore his nephew, Sejo abolished the Hall of Worthies and executed Danjong along with several ministers who served during Sejong's reign.
Sejong the Great is considered one of the most influential monarchs in Korean history, with the creation of Hangul considered his greatest legacy. Sejong is widely renowned in modern-day South Korea. In a 2024 survey by Gallup Korea, Sejong was nominated as the second most respected figure by South Koreans, only to be surpassed by Yi Sun-sin. The Encyclopedia of Korean Culture evaluates the reign of Sejong "the most shining period of the history of our [the Korean] people." Sejong's creation of the Korean alphabet is celebrated every 9 October as Hangul Day, a national holiday.
Multiple places in South Korea, including Sejong Street (Sejongno; 세종로, 世宗路), Sejong–Pocheon Expressway, and Sejong Special Autonomous City, South Korea's de facto administrative capital, are named after him. Various institutes such as King Sejong Station, the King Sejong Institute, the Sejong Center for the Performing Arts, Sejong Science High School, and Sejong University also bear his name. A 9.5-meter-high (31 ft) bronze statue of King Sejong, unveiled in 2009 in celebration of the 563rd anniversary of the invention of the Korean alphabet, now sits on a concrete pedestal on the boulevard of Gwanghwamun Square and directly in front of the Sejong Center for the Performing Arts in Seoul. The pedestal contains one of the several entrances to the 3,200 m underground museum exhibit entitled "The Story of King Sejong". In 2007, the South Korean Chief of Naval Operations officially announced the naming of its Sejong the Great-class destroyers, further explaining that Sejong's name was chosen as he was the most beloved figure among South Koreans. A portrait of Sejong is featured on the 10,000-won banknote of the South Korean won, along with various scientific tools invented under his reign. Sejong was first portrayed in the 1000-hwan bill as part of the 15 August 1960 currency reform, replacing the portrait of former president Syngman Rhee. Sejong was also featured on the 500-hwan bill the following year. Both bills were decommissioned in 1962. Sejong's portrait returned with the introduction of the 10,000-won bill, when his portrait and Geunjeongjeon replaced Seokguram and Bulguksa as features of the bill, in 1973.
In North Korea, Sejong is not as widely commemorated as in the South. Volume 16 of the Great Korean Encyclopedia asserts that feudalist pressure and extortion was strengthened during Sejong's reign and that all of Sejong's policies were directed for the benefit of the feudalist ruling class. In contrast, on 15 December 2001, North Korean news outlet Tongil Sinbo stated in a column that Sejong the Great greatly contributed to Korean science during his 30-year reign. Hangul Day is also celebrated in North Korea, albeit on a different date than in South Korea.
Sejong and his primary consort Soheon had ten children together: the most for any queen consort of the Joseon period. Historian Lee Han argues it is unclear if their relationship had genuine love; while they had numerous children together, and there is evidence of the two caring for and treating each other respectfully, Taejong had the queen's father executed, and Sejong dutifully consented to this.
His life was depicted in the KBS historical drama The Great King, Sejong in 2008.