Okada Izo (?? ??, February 14, 1838 – June 3, 1865) was a Japanese samurai of the late Edo period, feared as one of the four most notable assassins of the Bakumatsu period.
He was born in Tosa to the goshi Okada Gihei, who had been a peasant but had bought the goshi rank.
Izo and Tanaka Shinbei were active in Kyoto as assassins under the leadership of Takechi Hanpeita.
He was involved in the killing of Homma Seiichiro.
In 1865 however, he was involved in yet another assassination, that of Yoshida Toyo, the regent of Tosa whom he killed before his rise to power.
Izo was captured, tortured and beheaded by government forces on June 3rd, 1865.