Saito Dosan (斎藤 道三 1494-1556) was the epitome of the daimyo that dramatically rose and also fell from power in Sengoku period Japan. He is known as Mamushi(a type of poisonous snake) of Mino for his ruthless tactics.

Originally a wealthy merchant from Yamashiro province (Kyoto), he used his power and influence to become a retainer of the daimyo Toki Yorinari of Mino province (Gifu prefecture). Dosan eventually succeeded in becoming the magistrate of Mino and settled in Inabayama castle. Exploiting his power and wealth, he drove Toki Yorinari out of Mino province in a Coup d'etat in 1542 and claimed the fief as his own, becoming a daimyo in his own right. Afterwards, Toki Yorinari allied with Oda Nobuhide of Owari province just south of Mino to avenge Dosan, but their defeat at the battle of Kanoguchi in 1547 solidified Dosan's domination of Mino and also made a name for himself throughout Japan. The defeated Oda Nobuhide made peace and arranged a political marriage in 1549 between his son Oda Nobunaga and Saito's daughter to end all hostilities.

Ironically, Saito Dosan fell in his own son Saito Yoshitatsu's coup d'etat in 1556. Heavily outnumbered, he was defeated at the Battle of Nagara River.

Saito Dosan is known for large number of alias and frequent change of his name. Some believes that this is because there were two Saito Dosan, father and son, and son adopted his father's name after his death. Other names of Saito Dosan are Minemaru (峰丸), Horenbo (法蓮坊), Matsunami Shogoro (松浪庄五郎), Nishimura Kankuro Masatoshi (西村勘九郎正利), Shinkuro (新九郎), Nagai Norihide (長井規秀), and Saito Sakondayu Toshimasa (斎藤左近大夫利政).

ja:斎藤道三