The House of Yi, also called the Yi dynasty (also transcribed as the Lee dynasty), was the royal family of the Joseon dynasty and later the imperial family of the Korean Empire, descended from the Joseon founder Yi Seong-gye. All of his descendants are members of the Jeonju Yi clan.
After the Japan–Korea Treaty of 1910, in which the Empire of Japan annexed the Korean Peninsula, some members of the Jeonju Yi clan were incorporated into the Imperial House of Japan and the Japanese peerage by the Japanese government. This lasted until 1947, just before the Constitution of Japan was promulgated. The treaty was nullified in the Treaty on Basic Relations between Japan and the Republic of Korea.
With the Constitution succeeding to the Provisional Government, the descendants of the Imperial Family continue to be given preference and constitute a favored symbol in South Korea. The July 2005 funeral of Yi Ku, former head of the royal household, attracted considerable media coverage. Yi Seok also caught attention as of the 100th anniversary of Korean independence on March 1, 2019.
When Taejo of Joseon ascended to the throne in 1392, he continued to use the laws of Goryeo, and the noble titles he gave to his sons, nephews, and sons-in-law were all "prince" (군). After the coup d'état in 1398, the system of noble titles changed: "duke" for king's sons, "marquis" for royal descendants, and "earl" for officers of senior first rank. This system was abolished in 1401 to avoid "usurping" the existing title laws of the more powerful Ming dynasty.
As of 1412, Taejong of Joseon approved a new system for giving titles to the royalty: among the sons of a king, those who were born by the queen can acquire the title "grand prince" (대군), and the rest can be the "prince" (군); both princes are of senior first rank and their male descendants are as well insofar as their great-grandsons can retrieve official positions. According to the Veritable Records of the Joseon Dynasty, the title "prince" (군) was at first restricted to be given to sons or grandsons of kings, but these standards became looser over time.