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.^{[citation needed]}

On 28 July 1392, when Taejo made a new dynasty, he was granted the royal title King Mok (목왕; 穆王).^[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 (목조; 穆祖) by his great-great-great-grandson, King Taejong on 22 April 1411 along with his posthumous name.^[2]

• Father: Yi Yang-mu (이양무; 1186–1231)
  • Grandfather: Yi Rin (이린; 1150–?)
  • Grandmother: Lady Mun of the Nampyeong Mun clan (남평 문씨; 1149–?); third daughter of Mun Geuk-gyeom (문극겸; 1122–1189).
• Mother: Lady Yi of the Samcheok Yi clan (삼척 이씨; 1182–?)
  • Grandfather: Yi Gang-je (이강제; 1161–1260)
    • Older brother: Yi An-in (이안인; 1202–?)
    • Younger brother: Yi Yeong-pil (이영필; 1205–?)
    • Younger brother: Yi Yeong-mil (이영밀; 1206–?)
    • Younger brother: Yi Yeong-seup (이영습; 1208–?)
• Wife: Queen Hyogong of the Pyeonchang Yi clan (효공왕후 이씨; 1207–?)
  • First son: Yi Eo-seong, Grand Prince Ancheon (이어선 안천대군; 1230–1274)
  • Second son: Yi Jin, Grand Prince Anwon (이진 안원대군; 1232–?)
  • Third son: Yi Jeong, Grand Prince Anpung (이정 안풍대군; 1234–?)
  • Fourth son: Yi Haeng-ni (이행리 익조대왕; 1236–?)
  • Fifth son: Yi Mae-bul, Grand Prince Anchang (이매불 안창대군; 1238–?)
  • Sixth son: Yi Gu-su, Grand Prince Anheung (이구수 안흥대군; 1240–?)

• 목조 on the Encyclopedia of Korean Culture (in Korean).