So Sadakuni
- Other Names: 国分寺殿 (Kokubunji dono)
- Japanese: 宗 貞国 (Sô Sadakuni)
Sô Sadakuni was the tenth head of the Sô clan. He held that position from 1468 until 1492. His time saw the relocation of the clan's territory from Saga (on the island of Kyushu) to Tsushima Fuchû (Izuhara), on the island of Tsushima.[1]