The was a Japanese samurai clan which was one of the most powerful of the Muromachi period (1336-1467); at its peak, members of the family held the position of Constable (shugo) over eleven provinces. Originally from Kōzuke Province, and later centered in Inaba province, the clan claimed descendance from the Seiwa Genji line, and from Minamoto Yoshishige in particular. The clan took its name from the village of Yamana in present-day Gunma Prefecture. They were valued retainers under Minamoto no Yoritomo, and counted among his gokenin.