The Mogami Yoshiaki Historical Museum is located in Yamagata City, Yamagata Prefecture, which was headquartered by the Mogami clan from the period of the Northern and Southern Courts (Japan) to the early Edo period, and the museum contains historical documents regarding mainly the 11th family head, Yoshiaki MOGAMI.
最上氏が南北朝時代(日本)から江戸時代初期にかけて拠点とした山形県山形市に、最上義光歴史館があり、第11代当主・最上義光を中心とした資料が集められている。