King Munjong, previously known as Crown Prince Hwiji (Hanja: 文宗王 (輝之世子); Born: November 15th 1414 – Died: June 1st 1452; Reigned: 1450-1452), born Yi Hyang (이향/李珦) was the fifth King of the Joseon Dynasty. He was the eldest son of King Sejong the Great and Queen Soheon of Cheongsong Shim Clan and succeeded him in 1450, but died of disease two years later. He was succeeded by his son, King Danjong the Young a.k.a Yi Hong-wi.
Most of Munjong's achievements were performed during his princely life. Although credited is primarily given to Jang Yeong-sil for inventing the water gauge, the Annals of the Joseon Dynasty state that it was the Crown Prince who found measures of water levels in the ground. Also, it was Munjong who took care of state affairs late during King Sejong's reign, as Sejong developed various illnesses and disorders (i.e: Diabetes).
Munjong was the longest holder of the position of Crown Prince during the Joseon Dynasty, holding the position from 1421 to 1450, a record 29 years. From 1442 until his own accession to the throne in 1450, he served as regent to King Sejong.
King Munjong was buried at the Royal Tomb of Hyeolleung (顯陵), part of Donggureung Royal Tomb Cluster in 197 Donggureung Avenue/Donggureungno, Inchang-dong san 6-3 beonji, Guri City, Gyeonggi Province. He was posthumously known as King Munjong Gongsun Heummyeong In-sook Gwangmun Seonghyo the Great (문종공순흠명인숙광문성효대왕/文宗恭順欽明仁肅光文聖孝大王).