Yi Un
Crown Prince of Korea
Yi Un as a lieutenant of the IJA, 1920s
Head of the House of Yi
Period	24 April 1926 – 1 May 1970
Predecessor	Emperor Sunjong
Successor	Crown Prince Yi Ku
Born	(1897-10-20)20 October 1897 Deoksugung, Seoul, Korean Empire
Died	1 May 1970(1970-05-01) (aged 72) Nakseon Hall, Changdeokgung, Seoul, South Korea
Burial	Yeongwon Hongneung, Namyangju, South Korea
Spouse	Princess Masako of Nashimoto of Japan ​ ​ (m. 1920⁠–⁠1970)​
Issue	Prince Yi Jin Crown Prince Yi Ku of Korea
Names Yi Un (이은; 李垠) Posthumous name Crown Prince Uimin (의민황태자; 懿愍皇太子)
House	Yi
Father	Emperor Gojong of Korea
Mother	Imperial Noble Consort Sunheon
Military career
Allegiance	Japan
Service / branch	Imperial Japanese Army
Years of service	1917–1945
Rank	Lieutenant General
Unit	North China Area Army Chosen Army Inspectorate General of Military Training Supreme War Council
Commands	Imperial Guards 2nd Brigade 51st Division First Air Army
Battles / wars	Second Sino-Japanese War Second World War
Awards	Grand Cordon of the Supreme Order of the Chrysanthemum

Yi Un^[a] (Korean: 이은; 20 October 1897 – 1 May 1970) was the 28th Head of the Korean Imperial House, an Imperial Japanese Army general and the last Imperial Crown Prince of the Korean Empire. Before becoming the heir apparent to Sunjong of Korea, who became the emperor in 1907, Yi Un was known as the title Prince Imperial Yeong (영친왕). In 1910, the Korean Empire was annexed by Japan and Emperor Sunjong was forced to abdicate, and Yi Un married Princess Masako of Nashimoto, the eldest daughter of Prince Nashimoto Morimasa, on 28 April 1920 at Tokyo.

On 10 June 1926, upon the death of Emperor Sunjong, Yi Un received the late emperor's title, and became the King Yi of Changdeokgung (昌徳宮李王), which referred to the palace Changdeokgung. He achieved the rank of Lieutenant General in the Imperial Japanese Army, commanded Japanese forces in China and served as a member of the Supreme War Council. After World War II he was refused entry to Korea, and his Japanese titles were removed by article 14 of the new Constitution of Japan in 1947. After his death in 1970, Yi Un is alternatively known as Crown Prince Uimin (의민태자), a posthumous name given by the Jeonju Lee Royal Family Association.

The prince was born on 20 October 1897 at Deoksugung in Seoul as the seventh son of Gojong, the Gwangmu Emperor. His mother was the Honorable Princess Consort Eom Seon-yeong, a palace attendant, who was posthumously awarded the title of Princess Sunheon. He was also the younger half-brother of Emperor Sunjong and Prince Imperial Ui. He was titled Prince Imperial Yeong in 1900, and became the crown prince in 1907, despite being younger than Prince Ui. Prince Ui's support base at court was not strong because his own mother, Lady Jang, had already died.

In December 1907, he was taken to Japan on the initiative of Itō Hirobumi to be enrolled at Gakushūin Peers' School. The move was meant to ensure that the Korean royal family would not take any further anti-Japanese actions following The Hague Secret Emissary Affair.^[1] Japanese Emperor Meiji, who largely ignored his own grandchildren, devoted a lot of attention to Yi Un, acting as his guardian.^[1] Itō would bring Yi Un whenever he was visiting the princes Hirohito, Chichibu and Takamatsu.^[1] Meiji apparently stopped seeing Yi Un so frequently after Ito's assassination.^[2] Yi Un was allowed to visit Korea again only after the death of his mother in 1911.^[1]

In September 1911, the prince was enrolled in the second year of the Army Central Youth School, a military preparation school located in Tokyo. He was poor in gymnastics due to his small stature, but excelled in music and martial arts. He was then enrolled in the 29th class of the Imperial Japanese Army Academy, from which he graduated on 25 May 1917 with an excellent record.

He was commissioned a second lieutenant in the infantry on 25 December, and steadily rose up the ranks, receiving promotions to lieutenant (April 1920), and captain (July 1923). He graduated from the 35th class of the Army Staff College in November 1923 and commanded a battalion of the Guards 2nd Infantry Regiment. He was assigned to the Imperial Japanese Army General Staff Office in December 1924, and to the staff of the Chosen Army in July 1926. In 1926, he visited Korea in order to visit Sunjong of Korea with his wife.^[3] In May 1927, he was sent on an extensive European tour, visiting France, Switzerland, United Kingdom, Belgium, Netherlands, Germany, Denmark, Norway, Sweden, Poland, Austria, Czechoslovakia, Italy, Monaco, and returning to Japan in April 1928. In August, he was promoted to major and in August 1929 became commander of the IJA 1st Infantry Regiment. In December 1930, he was assigned to the Inspectorate General of Military Training and was promoted to lieutenant colonel in August 1932. He became colonel in August 1935 and commanded the Utsunomiya-based IJA 59th Infantry Regiment. From April 1937, he served as an instructor at the Army Academy.

In July 1938, the prince was promoted to major general and from December was assigned to the staff of the North China Area Army, which was engaged in combat operations in northern China following the start of the Second Sino-Japanese War. Throughout the first half of 1939, he made extensive inspection tours of front-line units throughout northern Japan, and reviewed Kwantung Army garrison units in Manchukuo. In August, he was appointed commander of the Guards 2nd Brigade and in May 1940 was commander of the reserve Fourth Depot Division. He was promoted to lieutenant general in December. In July 1941, he was appointed commander of the IJA 51st Division also based in Utsunomiya.

Under his command, the division relocated to Manchukuo to participate in the Special exercise of the Kwantung Army (actually a mobilization for the possible large-scale conflict with the Soviet Union). The preparations for the war with the Soviet Union were officially cancelled in August 1941. In September, the division was transferred to Guangdong under command of IJA 23rd Army. He returned to a post on the staff of the Inspectorate General of Military Training in November.

From August 1942, the prince was transferred to the Imperial Japanese Army Air Force and became commander of the 1st Air Army from July 1943. In April 1945, he became a member of the Supreme War Council.^[4]

Following the surrender of Japan, Yi Un lost his royal status under the American Occupation of Japan in 1947. He was also declared stateless, as Korea had become independent of the Empire of Japan, but Korean President Syngman Rhee had refused his request to be allowed to return to Korea with his family. In May 1947, following the end of the American occupation, he acquired Japanese citizenship and travelled to the United States the same month. In March 1959, while still in the United States, he suffered from a stroke. He returned to Japan in May. In 1960, President Rhee again denied him permission to return to Korea, but instead offered the prince the position of Korean Ambassador to the Court of St. James's. He refused on the grounds of illness, but made a trip to New York from June to August 1960, and to Hawaii from March to May 1961. His health deteriorating rapidly, he was hospitalized in Tokyo from August 1961.

In November 1963, President Park Chung Hee granted permission for Prince Yi Eun and Crown Princess Bangja to return to Korea. By that time, Prince Yi Eun was unconscious from cerebral thrombosis. He received treatment at St. Mary's Hospital in Seoul.

In his final years, Prince Yi Eun lived at Nakseon Hall, Changdeok Palace, the former residence of the Korean Imperial Family in Seoul, with Bangja and his younger sister Princess Deokhye. Seven years after returning to his country, he died on 1 May 1970 at Nakseon Hall, Changdeok Palace, Seoul. He was buried at Hongreung in Namyangju, near Seoul.

• Yi Jin (이진; 李晋; I Jin; I Chin; born 18 August 1921 – 11 May 1922), the elder son of Prince Eun and his wife, Princess Bangja. Yi Jin died abruptly during his infancy while on a visit to Korea with his parents. This fueled conspiracy theories about the circumstances of his death. His funeral was held on 17 May 1922 and he is buried in Korea.
• Yi Gu (이구; 李玖; I Gu; I Ku; born 29 December 1931 – 16 July 2005), the second son of Prince Eun and his wife, Princess Bangja. Prince Gu became the 29th Head of the Korean Imperial Household upon the death of his father. He married an American citizen Julia Mullock on 25 October 1959 at St George's Church in New York, they had no issue but adopted a daughter, Eugenia Unsuk Lee (Eun-sook) (b. 1959).

•  Korean Empire: Grand Cordon of the Order of the Golden Ruler - 17 April 1900
•  Empire of Japan: Grand Cordon of the Order of the Rising Sun, with Paulownia Flowers – 17 October 1907^[5]
•  Denmark: Grand Cross of the Order of the Dannebrog – 10 November 1927^[6]
•  Sweden: Commander Grand Cross of the Order of Vasa, with Collar – 13 November 1927^[7]
•  Czechoslovakia: Grand Cross of the Order of the White Lion – 16 December 1927^[8]

Yi Un is known posthumously as Yi Un, Crown Prince Euimin of Korea. Approved by the President Park Chung Hee, Yi Un's spirit tablet was put into Jongmyo shrine on 6 May 1973 according to the royal tradition.^[9]

Yi Un's residence Kitashirakawa Palace in Tokyo was originally built in 1930. After World War II, it was converted to Akasaka Prince Hotel, which opened in 1955 (later Grand Prince Hotel Akasaka). After the hotel was demolished in 2013, the building became part of Tokyo Garden Terrace Kioicho, refurbished as a banquet facility, now known as Akasaka Prince Classic House.

• Portrayed by Park Soo-young in the 2016 period drama film The Last Princess.