Crown Prince Sado (Korean: 사도세자; Hanja: 思悼 世子; 13 February 1735 – 12 July 1762), personal name Yi Seon (이선; 李愃), was the second son of King Yeongjo of Joseon.

However, at the age of 27, he died, most likely of dehydration and possibly of starvation after being confined in a rice chest on the orders of his father in the heat of summer.

[6] Yeongjo also did not permit Sado to visit the ancestral tombs until as late as 1756, nor was he allowed to attend auspicious court events.

[8] As a result, Sado formed a strong bond with his sister Princess Hwahyeop, who was similarly disfavoured by their father.

[8] In the same month as the burial of Queen Jeongseong, Sado walked into his chambers holding the severed head of a eunuch whom he had killed, forcing the ladies-in-waiting and his wife to view it.

[16] On his birthday in 1760, Sado suffered a burst of outrage at his parents, berating his mother Lady Yeong-bin, as well his own son, and two daughters.

[17] After this, he demanded that Princess Hwawan use her influence over King Yeongjo to move palaces and allow Sado to visit the springs at Onyang.

[19] While Lady Hyegyŏng said he was not violent to her, she also noted he would beat any women who resisted his sexual overtures until he "rent their flesh" and they gave in.

There was one documented incident where Sado was physically violent toward his wife, in which he threw a go board at her face and made it necessary for Lady Hyegyŏng to avoid court events to hide the bruises.

[24] By court rules, the body of a royal could not be defiled and, under the then-common practice of communal punishment, Sado's wife and son (the family's only direct male heir) could also face death or banishment if he were executed as a criminal and traitor.

After two days, King Yeongjo had the chest containing Sado tied with rope, covered with grass, and moved to the upper palace.

[29] Yeongjo then restored him to the position of crown prince and gave him the posthumous title Sado, meaning "thinking of with great sorrow".

His body was moved by his son, King Jeongjo, to its current location in 1789, then called Hyeonnyungwon near Suwon, 30 kilometres south of Seoul.

Five years later the Hwaseong Fortress was built by King Jeongjo, specifically to memorialize and honour his father's tomb (the construction lasted from 1794 to 1796, while the official reception was 1795).