Grand Prince Yangnyà Âng (; 1394 â 8 October 1462) was the former Crown Prince of the Korean Joseon Dynasty. He was the first son of King Taejong and his wife, Queen Wongyeong. Yangnyà Âng was the elder brother of Sejong the Great, and an ancestor of Syngman Rhee, an independence activist and the first President of South Korea.
He was born as Yi Che () in 1394. Originally his father appointed him as crown prince but he eventually executed Queen Wongyeong's brothers and in the 18th year of his reign replaced Prince Yangnyà Âng with his third son Prince Chungnyeong as heir apparent. Known for his literature and calligraphy skills, the former crown prince lacked in the requisite skills for kingship and acted extremely rude in court. On May 1415, he caused a scandal when he had an affair with Chogungjang, the kisaeng of his uncle and former king, Jeongjong. Yangnyà Âng was unaware that Chogungjang was his uncle's woman. On 15 February 1417, Yangnyà Âng secretly brought in Eori, the concubine of Gwak Seon, into the palace. Angered, Taejong banished Yangnyà Âng from the royal palace to the residence of Yangnyà Âng's father-in-law, Kim Han-ro. However, Kim Han-ro arranged a rendezvous between Yangnyà Âng and Eori, and Eori bore the crown prince's child. For a while, Taejong did not fault Yangnyà Âng for his libertine proclivities but instead held his father-in-law, Kim Han-ro, accountable for Crown Prince Yangnyà Âng's improprieties.
The final event that sealed Yangnyà Âng's fate was a letter he wrote to Taejong, accusing Taejong of hypocrisy. Yangnyà Âng criticized his father for punishing him over his affair with Eori, while Taejong himself maintained ten concubines, in direct violation of the Confucian virtue of highest importance: filial piety. Due to Yangnyà Âng's continued lack of remorse, Taejong deposed Yangnyà Âng as crown prince on 3 June 1418. Sorrowful, Taejong asked two officials who had been sent to inform Yangnyà Âng of his deposition about Yangnyà Âng's reaction. They reported back to Taejong that Yangnyà Âng neither cried nor showed signs of sadness. Yangnyà Âng was banished from the palace and relocated to Gwangju. Taejong initially considered to create two sons of Yangnyà Âng his new heir, but finally chose his own third son Grand Prince Chungnyeong, the later Sejong.
After Sejong became king, the relationship between the brothers strengthened, with Sejong often inviting Yangnyà Âng to the palace. During Sejo's reign, Yangnyà Âng enjoyed the status of the eldest royal family member, and Sejo often invited Yangnyà Âng to the palace for court revelries.
Yangnyà Âng died in 1462, the eighth year of Sejo's reign, at the age of 68.
The tomb of Prince Yangnyà Âng reopened in 2018 to the public after 18 years of closure.