Neo-Confucian scholar regarded as a forerunner of the Yeongnam school, enshrined in both the Confucian Shrine and the royal ancestral shrine; pen name Hoejae; posthumous title Munwon

| Life | 1491 ~ 1553 |
| Era | 조선 중기 |
| Clan | 여주 이씨 |
Yi Eon-jeok (1491-1553) was a mid-Joseon official and Neo-Confucian scholar. His seat is Yeoju (also written Yeogang), and he belonged to the Gyeongju branch, in the 11th generation. His courtesy name was Bokgo, pen names Hoejae and Jagyeong-ong, and posthumous title Munwon. Born in Yangdong Village, Gyeongju, he lost his father early and was raised by his maternal uncle Son Jung-don; he passed the civil examination in 1514. In 1517 he joined the Mugeuk-Taegeuk debate, arguing from Zhu Xi's priority of principle (li), which is regarded as the first philosophical debate of Joseon Neo-Confucianism.
After the Literati Purge of 1519 he declined court posts and asked for provincial ones, serving as magistrate of Indong and Miryang. Dismissed in 1531 for opposing the appointment of Kim An-ro, he built Dongnakdang on Mt. Jaok and devoted himself to study; he returned after Kim's fall in 1537, was chosen as an incorruptible official in 1538, and rose through Inspector-General, Vice-Director of the Hongmungwan, Minister of Personnel, Punishments and Rites, and Governor of Gyeongsang, becoming Left Vice Premier under King Injong.
In 1547 he was falsely implicated in the Yangjae Station placard affair and exiled to Gangye in North Pyongan, where he wrote works including the Daehak Jangguibo-yu and Guinrok and died in 1553 while writing the Jungyong Gugyeong Yeon'ui. He was posthumously made Chief State Councillor in 1568, enshrined in King Myeongjong's ancestral hall in 1569 and in the Confucian Shrine in 1610 as one of six sages honored in both shrines.
In the 1517 debate Yi Eon-jeok held that principle (li) precedes material force (gi) and that the two are not mixed. This view passed to Yi Hwang and is seen as a basis of the Yeongnam school; Yi Hwang regarded him as a spiritual teacher and wrote his conduct record.
His works include the Guinrok on benevolence, the Daehak Jangguibo-yu rearranging Zhu Xi's edition, the ritual text Bongseon Japui, and the unfinished Jungyong Gugyeong Yeon'ui written at Gangye. His rereading of the Great Learning later drew controversy.
At the 1519 purge he left the court for a provincial post; at the 1545 purge he sat as an interrogating official and gave lenient judgments, later drawing criticism and suspicion. Yi I criticized him for failing to keep his integrity, while others see someone who sought moderate solutions without compromising with injustice. His dismissal for opposing Kim An-ro's appointment is often cited as a sign of his uprightness.
He was enshrined at Oksan Seowon in Gyeongju in 1573 (with a royal plaque) and in the Confucian Shrine in 1610. Dongnakdang and Oksan Seowon are leading sites of the Gyeongju branch near Angang, and Yangdong Village, a UNESCO World Heritage site, is its chief ancestral village.
His tomb and spirit-path stele are at Daljeon-ri, Yeongil-eup, Nam-gu, Pohang; the stele is a North Gyeongsang tangible cultural property.
Five sons of his adopted heir Yi Eung-in founded the Mucheomdang, Yangjoldang, Seolcheonjeong, Sujoldang and Oui-jeong lines, while descendants of his illegitimate son Yi Jeon-in formed the Guam-gong and Chiam-gong lines at Oksan.