The Oshu Fujiwara clan was the clan whose power stretched over the entire Tohoku region, which centered on Hiraizumi in Mutsu Province (later Rikuchu Province) and included Dewa Province, from 1087 after the Zenkunen War (the Early Nine Years' War) and the Gosannen War (the Later Three Years' War) to 1189, when it was destroyed by MINAMOTO no Yoritomo.
奥州藤原氏（おうしゅうふじわらし）は前九年の役・後三年の役の後の寛治元年（1087年）から源頼朝に滅ぼされる文治5年（1189年）までの間、陸奥国（後の陸中国）平泉を中心に出羽国を含む東北地方一帯に勢力を張った一族である。