Yantra (यन्त्र) (literally "machine, contraption") is a geometrical diagram, mainly from the Tantric traditions of the Indian religions. Yantras are used for the worship of deities in temples or at home; as an aid in meditation; used for the benefits given by their supposed occult powers based on Hindu astrology and tantric texts. They are also used for adornment of temple floors, due mainly to their aesthetic and symmetric qualities. Specific yantras are traditionally associated with specific deities and/or certain types of energies used for accomplishment of certain tasks, vows, that may be materialistic or spiritual in nature. It becomes a prime tool in certain sadhanas performed by the sadhaka the spiritual seeker. Yantras hold great importance in Hinduism, Jainism, and Buddhism.

Representations of the yantra in India have been considered to date back to 11,000–10,000 years BCE. The Baghor stone, found in an upper-paleolithic context in the Son River valley, is considered the earliest example by G.R. Sharma, who was involved in the excavation of the stone (it was dated to 25,000 - 20,000 BCE). The triangular stone, which includes triangular engravings on one side, was found daubed in ochre, in what was considered a site related to worship. Worship of goddesses in that region was found to be practiced in a similar manner to the present day. Kenoyer, who was also involved in the excavation, considered it to be associated with Shakti. This triangular shape looks very much similar to Kali Yantra and Muladhara Chakra.

Mantras, the Sanskrit syllables inscribed on yantras, are essentially "thought forms" representing divinities or cosmic powers, which exert their influence by means of sound-vibrations.