| Yi Ansa 이안사 李安社 | |
| King of Joseon (posthumously) | |
| Succession: | Darugachi |
| Reign: | 1252–1274 |
| Birth Name: | Yi Ansa (이안사) |
| Birth Date: | 1204 |
| Birth Place: | Jeonju, North Jeolla Province, Goryeo |
| Death Date: | 3 March 1274 (aged 69-70) |
| Death Place: | Jeonju, North Jeolla Province, Goryeo |
| Burial Place: | Deokneung tomb |
| Spouse: | Queen Hyogong (m. 1223) |
| Issue: | 6 sons |
| Posthumous Name: |
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| Temple Name: | Mokjo (목조, 穆祖) |
| Royal House: | House of Yi |
| Father: | Yi Yang-mu |
| Mother: | Lady Yi of the Samcheok Yi clan |
Yi An-sa (1204 – 3 March 1274) was a Goryeo nobleman who would become the great-great-grandfather of Yi Seonggye, founder of the Joseon Dynasty.
On 28 July 1392, when Taejo made a new dynasty, he was granted the royal title King Mok .[1] After his death in 1274, he was buried in Deokneung, Neung-ri, Gapyeong-myeon, Sinhung-gun, South Hamgyong Province, North Korea and given the temple name Mokjo by his great-great-great-grandson, King Taejong on 22 April 1411 along with his posthumous name.[2]