Founding ancestor of the Haeju O clan
| Era | 고려 |
| Clan | 해주 오씨 |
O In-yu, founding ancestor of the Haeju O clan, was originally a Song dynasty Chinese scholar who naturalized to Goryeo in 984 during King Seongjong's reign, served as inspector of military supplies, and settled in Haeju.
The Haeju O clan later split into two lines tracing descent from O In-yu and from O Hyeon-bo respectively. Among O In-yu's descendants, fourteenth-generation descendant O Yun-gyeom became Chief State Councillor under King Injo of Joseon, and O Yun-gyeom's own great-great-grandson, O Myeong-hang, rose to State Councillor of the Right, cementing the clan's standing among Joseon's leading official families.
It produced many civil officials in the Joseon period, such as O Yun-gyeom.