Fudo (Fudō-Myōō) is the Japanese incarnation of the Buddhist deity Acala, "The Immovable One," the destroyer of delusion and the protector of wisdom teachings.

Fudo is the central deity of the Great Myo, the Japanese term for the Sanskrit Vidyaraja, a group of wrathful, warlike deities known in English as the Wisdom Kings.

In contrast to the saintly images of Buddhas and Bodhisattvas, images of the Myo are ferocious and menacing; their threatening postures and contorted grimaces are expressions of the force with which they strive to dispell ignorance and strengthen the will of those who seek liberation. They are often depicted engulfed in flames, representing the purification of the mind by the burning away of all attachment and shadow.

The Myo carry vicious weapons to protect practitioners and destroy corrupting influences. Fudo is armed with a rope in his left hand for capturing and binding demons, and a sword of wisdom for subduing demons and cutting through ignorance in his right. From his mouth protrude two fangs, one pointing down, representing his compassion and concern for suffering beings; and one pointing upward, representing his passion for wisdom in transcendence. Centered within, Fudo embodies the seed of awakening.

Fudo expresses the ability to transform the heat of anger into the energies of excellence, an attribute that makes him immovable in his commitment to aiding all beings on the path to self-control and liberation.