| Yi Haeng 이행 | |
| Succession: | Crown Prince of Joseon |
| Reign: | 7 April 1725 – 16 December 1728 |
| Reign-Type: | Tenure |
| Predecessor: | Crown Prince Yi Yun |
| Successor: | Crown Prince Yi Seon |
| Birth Date: | 4 April 1719 |
| Birth Place: | Prince Yeoning's private residence, Hanseong, Joseon |
| Death Place: | Jinsudang Hall, Changgyeong Palace, Hanseong, Joseon |
| Burial Place: | Yeongneung Tombs, Samneung Cluster, Paju, Gyeonggi Province, South Korea |
| House-Type: | Clan |
| Father: | Yeongjo of Joseon |
| Mother: |
|
| Religion: | Neo-Confucianism |
| Dynasty: | House of Yi |
| Spouse: | Crown Princess Hyosun |
| Issue: | Yi San, King Jeongjo of Joseon (adoptive) |
| Temple Name: | Jinjong (진종, 真宗) |
| House: | Jeonju Yi clan |
| Posthumous Name: |
|
| Hangul: | 효장세자 |
| Rr: | Hyojang Seja |
| Mr: | Hyochang Secha |
| Hangulborn: | 이행 |
| Rrborn: | I Haeng |
| Mrborn: | Yi Haeng |
| Korean name | |
| Hangul1: | 진종 |
| Rr1: | Jinjong |
| Hangulja: | 성경 |
| Othername1: | Temple name |
| Mrja: | Sŏngkyŏng |
| Rrja: | Seonggyeong |
| Mr1: | Jinchong |
Crown Prince Hyojang (; April 4, 1719 – December 16, 1728), personal name Yi Haeng, was the first son of King Yeongjo of Joseon and his concubine, Royal Noble Consort Jeong of the Hamyang Yi clan. In 1762, 34 years after his death, he became the adoptive father of his half-nephew, the future King Jeongjo.
Yi Haeng was the first son and second child of Yi Geum, Prince Yeoning (later King Yeongjo), by one of his concubines, Lady Yi of the Hamyang Yi clan, a former court lady.[1] He was born during the reign of his grandfather King Sukjong, but his birth was not made public, because his biological grandmother, Royal Noble Consort Suk, had died the previous year.
In 1720, King Sukjong was succeeded by his eldest son, Crown Prince Yi Yun (King Gyeongjong). As the new King was childless, his half-brother, Prince Yeoning, was appointed as Crown Prince .
Hyojang's biological mother, Lady Yi, died the following year.
In 1724, after the death of King Gyeongjong, Yeoning was crowned as King Yeongjo, the 21st Joseon monarch. Yi Haeng was then given the title Prince Gyeongui and in 1725, he was appointed as Crown Prince.
In 1726, Yeongjo selected Lady Jo of the Pungyang Jo clan, the only daughter of Jo Mun-myeong and a niece of Jo Hyeon-myeong, as his son's wife.
In 1728, the Crown Prince died in Changgyeong Palace, at the age of 9, after being ill for some months. The cause of his illness is unknown. His death was devastating to King Yeongjo, who later gave Yi Haeng the posthumous name Hyojang.
His wife, who was later honored as Queen Hyosun, outlived by more than two decades. They are buried together, in the Samneung Cluster, in Paju, Gyeonggi Province. Their tombs are known as Yeongneung.[2]
In 1735, seven years after his death, his half-brother Yi Seon (later known as Crown Prince Sado) was born and succeeded Hyojang as Crown Prince. In 1762, Sado was imprisoned in a wooden rice chest at the order of his father, King Yeongjo, and died 8 days later, leaving his son, Yi San, as the only royal male heir. Yeongjo was concerned that Yi San, being Sado's child, would be branded as "the son of a sinner" and thus become ineligible to succeed the throne, so in February 1764, he decreed that Yi San would become the adoptive son of the long-dead Crown Prince Hyojang.[3]
In 1776, King Yeongjo died of dementia and Yi San succeeded him as King Jeongjo. Surprisingly, on his coronation day, he announced to his courtiers, "I am the son of Crown Prince Sado".[4] In spite of this, Jeongjo respected the wishes of his grandfather and honored his adoptive father as King, and granted him the temple name Jinjong . Hyojang's wife, the late Crown Princess Hyosun, was also honored as Queen.
In 1907, Hyojang was elevated to Emperor So by Sunjong of Korea.
Consort(s) and their issue(s)