The homa is a votive offering involving the construction of a fire in a hearth-altar, and the immolation of offerings in the fire. The altar is homologized with a mandala, and as with other ritual uses of mandalas, the deity evoked in the course of the ritual is located at the mandala’s center, and in this case identified with the fire itself. As a tantric ritual, the practitioner is also ritually identified with both the deity and the fire, and the offerings made into the fire are the spiritual obstacles that impede the practitioner from full awakening. Tantric homas are generally categorized according to different functions or goals, such as protection, subduing adversaries, and so on. As a form of individual practice conducive to awakening, the practitioner’s own inherent wisdom is identified with the fire, and just as the offerings are transformed and purified, the practitioner’s own spiritual obstacles are as well. Ritualized activities of maintaining and making fire are some of the most ancient forms of social coordination, which is essential to the development of the human species. Such ritualization would seem to be the basis for fire cults, forms of which are known throughout the world’s religions. In the scope of Indo-European religions, similarities of practice and symbolism provide a shared background to the homa per se. More directly, there appear to be both Vedic and Indo-Iranian traditions of ritual praxis that converge in the tantric homa. The homa is found in all of the Indic tantric traditions: Buddhist, Śaiva, and Jain. Once established as part of tantric practice, the homa was spread throughout Central, East, and Southeast Asia, particularly in its Buddhist form. This transmission of ritual practice engaged local traditions wherever it spread. Tibetan tantric traditions developed an extensive literature of homa rituals, and from there the practice also influenced Mongolian fire rituals as well. In China, interaction between tantric Buddhism and Daoism led to the creation of a homa devoted to the Northern Dipper, a figure unknown in Indian sources of Buddhist tantra. Two similar examples are found in Japan. The Shintō traditions of Yuiitsu (or Yoshida) and Miwa modified the tantric Buddhist form for the worship of a selection of Shintō deities. Similarly, the tradition of mountain asceticism, Shugendō, also adopted the homa and adapted it to its purposes. As a result of the repression of Buddhism in the third quarter of the nineteenth century, the Shintō forms are no longer extant, though in the present many Shintō shrines perform rituals of various kinds in which fire plays an important role. In contrast, the Shugendō homa, sometimes as a prelude to fire-walking, remains an active part of Japanese religion into the present day. The tantric homa has been interpreted in a variety of ways, reflecting the multifaceted character of fire itself. There are two important strains of interpretation. One is the yogic interiorization of ritual found in post-Vedic Indian religion, more as a form of esoteric physiology than as a psychologized understanding of visualization. While closely related to yogic interiorization of ritual, the sexual symbolisms that are attached to all aspects of the fire rituals constitute a second strain of interpretation. These symbolic associations are important for their role in understanding tantric notions of ritual efficacy, which require greater nuance of understanding than can be attained by simply categorizing such practices as magic.