Vajra (Devanagari: वज्र, Chinese: 金剛 jīngāng; Tibetan རྡོ་རྗེ། dorje, Japanese: kongō 金剛) is a Sanskrit word meaning both thunderbolt and diamond. As a material device, the vajra is a ritual object, a short metal weapon—originally a kind of fist-iron like Japanese yawara—that has the symbolic nature of a diamond (it can cut any substance but not be cut itself) and that of the thunderbolt (irresistible force).

The vajra is believed to represent firmness of spirit and spiritual power. It is a ritual tool or spiritual implement which is symbolically used by Buddhism, Jainism and Hinduism, all of which are traditions of Dharma. Because of its symbolic importance, the vajra spread along with Indian religion and culture to other parts of Asia. It was used as both a weapon and a symbol in Nepal, India, Tibet, Bhutan, Siam, Cambodia, Myanmar, Indonesia, China, Korea and Japan.^{[citation needed]}