Founding ancestor of the Haeju O clan
| Era | 고려 |
| Clan | 해주 오씨 |
O In-yu (吳仁裕) is the founding ancestor of the Haeju O clan. A figure of around the reign of King Seongjong of Goryeo, he is said to have served as Geomgyo Gungigam (檢校軍器監) and others, and having settled at Haeju (海州) in Hwanghae Province, his descendants took Haeju as their ancestral seat.
The Haeju O clan is a representative ancestral seat among the O clans, having produced many civil officials, such as Chutan O Yun-gyeom, who served as Chief State Councillor in the Joseon period.
It produced many civil officials in the Joseon period, such as O Yun-gyeom.