Acala (Skr.: Ācala, Achala अचल; Ja: Fudō-myōō (不動明王?) literally "immovable" one.) is one of fierce, angry-faced guardian deities of Vajrayana Buddhism, otherwise known as esoteric Buddhism (mikkyō (密教?), and is particularly revered by Buddhists in Japan.

He is classed among the vīdyārāja (Ja: myōō ("wisdom king")), and preeminent among the Five Wisdom Kings of the Womb Realm. Accordingly, his figure occupies an important hierarchical position in the pictorial diagramatic Mandala of the Two Realms.

Read more about Acala:  Overview, History, Acala in Japan, Conflations and Confusions, In Popular Culture