| Hangul: | 이현운 |
| Hanja: | 李鉉雲 |
| Rr: | I Hyeonun |
| Mr: | I Hyŏnun |
Yi Hyŏn-un (;) was a Goryeo military commander. He was a subordinate of Kang Cho.
In 1009, Yi participated in Kang Cho's coup to destroy Kim Chi-yang's faction, dethrone King Mokjong and install King Hyeonjong. Prior to the coup, he was the vice military inspector of Seobukmyeon and the Vice Minister of Personnel .[1] After the coup, Kang Cho merged the Security Council, the Office of Transmission, and the Institute of Palace Miscellaneousness into the newly formed Palace Secretariat . Kang was appointed as the head of the Palace Secretariat, and Yi Hyŏn-un, as his deputy, was made its vice head.[2]
When the Khitan Liao invaded Goryeo in response to the coup in 1010, Yi became Kang's second-in-command, as the haengyŏng tot'ongbusa of the Goryeo army sent to fight the Khitans. Kang and Yi were both captured in battle and brought before Emperor Shengzong of Liao. Emperor Shengzong asked both men to defect and serve the Liao. While Kang Cho refused, Yi Hyŏn-un accepted. He told the emperor that "Now that I have seen the bright new sun and moon with my own two eyes, how could I persist to think of the old streams and mountains?"[3]