This groundbreaking work describes the historical origins of the Tantric movement in early medieval India. Drawing on primary documents -- translated into English for the first time from Sanskrit, Prakrit, and Bengali -- Davidson shows how changes in medieval Indian society, including economic and patronage crises, a decline in women's participation, and the formation of large monastic orders, led to the rise of the esoteric tradition in India that became the model for Buddhist cultures in China, Tibet, and Japan.