AbstractMahāmudrā, usually translated as ‘the great seal’, is a vital term in the tantric traditions of Buddhist India and most schools of Tibetan Buddhism. In early Indian Buddhist tantras, it refers primarily to a hand‐gesture (mudrā) accompanying visualization meditation. In the later and more esoteric Indian Mahāyoga and Yoginī tantras, it denotes, inter alia, one of a sequence of experiential ‘seals’ to meditation; a ‘consort’ in sexual yoga practices; and a non‐dual gnosis in which great bliss and awareness of emptiness (śūnyatā) are inseparably conjoined. In the songs and treatises of the Indian great adepts (mahāsiddhas), Mahāmudrā is an index of ultimacy, regarded as the luminous, empty nature of mind, i.e. our buddha‐nature; a type of meditation for realizing mind’s nature; a set of unconventional practices that express that realization; and the final fruit of meditation, buddhahood. In Tibet, Mahāmudrā was known during the imperial period, but gained prominence only during the Tibetan ‘renaissance’ that began in the 11th century. Although a topic of analysis in nearly every Tibetan tradition, it is most central to the Kagyü, or ‘oral lineage’. Introduced to the Kagyü by Marpa and Milarepa, Mahāmudrā was popularized by Gampopa, who analyzed it from many angles, and suggested it was as much a practice rooted in the sūtras as in the tantras. Subsequent Kagyü masters developed Gampopa’s analysis further, produced anthologies of Mahāmudrā texts, and related Mahāmudrā to a variety of important Indian and Tibetan Buddhist ideas and practices. As a meditation practice, Mahāmudrā often is divided into sudden and gradual approaches. The sudden approach involves simply abiding in the natural mind, which is tantamount to buddhahood. Gradual approaches may involve complex tantric visualizations and the manipulation of forces within the subtle body or a sequence of meditations that focus on the nature of mind, which is found to be empty, luminous, non‐dual, and blissful. Discourse on mahāmudra in India and Tibet raises a number of important issues for Buddhist thought and practice, such as the soteriological sufficiency of a single, sudden insight; the place of reason and ethics in contemplative tradition; and the unity or diversity of meditative realization. Those issues resonate, in turn, with discussions elsewhere of mysticism, religious experience, and the nature of mind.