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Yi Ku
Yi as a child
Head of the House of Yi
Period	May 1, 1970 – July 16, 2005
Predecessor	Crown Prince Yi Un
Successor	Yi Won orYi Seok orYi Hae-won (disputed)
Born	(1931-12-29)December 29, 1931 Kitashirakawa Palace (now formerGrand Prince Hotel Akasaka), Kioicho, Kojimachiku,Tokyo,Empire of Japan
Died	July 16, 2005(2005-07-16) (aged 73) Grand Prince Hotel Akasaka, Kioicho, Kojimachiku, Tokyo, Japan
Spouse	Julia Mullock ​ ​ (m. 1959; div. 1982)​
Issue	Eugenia Unsuk (adopted)
House	Yi
Father	Crown Prince Yi Un of Korea
Mother	Princess Masako of Nashimoto of Japan
Religion	Roman Catholicism
Occupation	Architect, businessperson

Yi Ku (Korean: 이구; December 29, 1931 – July 16, 2005) was a Korean prince who was head of theHouse of Yi from 1970 until 2005. He was a grandson ofEmperor Gojong of theJoseon dynasty. ThroughKuni Asahiko his maternal great-grandfather, Ku was a second-cousin to Emperor EmeritusAkihito of Japan.

Ku was born in Kitashirakawa Palace (which is currently the Akasaka Prince Classic House, formerly part of theAkasaka Prince Hotel), Kioicho, Kojimachiku,Tokyo,Japan; his parents wereCrown Prince Yi Un of Korea andYi Bangja. Ku attended theGakushuin Peers' School in Tokyo. He later attendedCentre College,Danville, Kentucky^[1] and studied architecture atMassachusetts Institute of Technology both in theU.S.

He was employed as an architect withI.M. Pei & Assocs,Manhattan,New York from 1959 to 1964. Madestateless byJapan in 1947, Ku acquiredUnited States citizenship in 1959 and South Korean citizenship in 1964. He marriedJulia Mullock (1927–2017) on 25 October 1959 at St George's Church in New York and they adopted a daughter, Eugenia Unsuk.

After the fall ofSyngman Rhee, he returned to Korea in 1963 with the help of the new presidentPark Chung Hee, moving into the New Building of Nakseonjae hall,Changdeokgung with his mother and wife. He lectured on architecture atSeoul National University andYonsei University and also managed his own airline, Shinhan. When that went bankrupt in 1979, he went to Japan to earn money. In 1982, his family forced him to divorce his wife because she was sterile; his mother died in 1989. He started living with a Japanese astrologer, Kinuko Arita. In November 1996, he decided to reside permanently in Korea.

Yi went back and forth between Japan and Korea, and eventually died of aheart attack, at the age of seventy-five, on July 16, 2005, at theAkasaka Prince Hotel, the former residence of his parents in Tokyo, Japan. His funeral was held on July 24, 2005, and his posthumous title decided as "Prince Imperial Hoeun" (Korean: 회은황세손;Hanja: 懷隱皇世孫) by theJeonju Lee Royal Family Association.^[2][3] He is buried at the Hoeinwon Royal Tomb near his father and mother.

Yi Ku did not have an heir. According to theJeonju Lee Royal Family Association,Yi Won, Yi Ku's first cousin once removed, was appointed as the heir by him. Yi Ku already considered adopting an heir for the imperial line of succession and Yi Won was considered; after meeting Yi Won several times, he was satisfied about the foreign language abilities of his cousin and allowed Won to be his successor. As of July 10, 2005, less than a week before his death, Yi Ku met the chairman of the association, Lee Hwan-ey (이환의;李桓儀),^[4] for the last time, and Yi Ku formerly signed to adopt Yi Won as his heir.^[5][6] Despite that Yi Ku died soon afterwards, the Jeonju Lee Royal Family Association held a meeting for the adoption legitimacy in July 21, and in the next day, July 22, 2005, Yi Won was officially recognized by the association to be the successor of late Yi Ku.^[7]

• Korean royalty
• Death announcement in Korea Times
• Farewell to royal heir evokes memories of Korea's past
• obituary in the English edition of Dong-A Ilbo

• 1929 births
• 2005 deaths
• Centre College alumni
• MIT School of Architecture and Planning alumni
• House of Yi
• American architects
• Japanese emigrants to the United States
• American people of Korean descent
• South Korean people of Japanese descent
• South Korean Roman Catholics
• Pretenders to the Korean throne
• Zainichi Korean politicians
• People from Chiyoda, Tokyo
• Korean anti-communists

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