This dissertation focuses on the life, writings, and thought of the Indian Buddhist yogin and tantric exegete Buddhajñānapāda, remembered as the founder of the Jñānapāda School of tantric theory and practice. Through an in-depth study of his oeuvre, I attempt to excavate the late eighth-century world of tantric Buddhism as it emerges in his narrative, doctrinal, and ritual writings. I focus, in particular, on his most important composition, the Dvitīyakramatattvabhāvanā-mukhāgama in which Buddhajñānapāda uses autobiographical narrative and visionary revelation to frame assertions about the nature of reality and outline rituals that lead to its realization. I examine the key features of both the doctrinal positions articulated in his works, as well as the ritual systems through which a yogin was to embody and realize those doctrines, showing that Buddhajñānapāda was an important and innovative figure in the realms of both tantric Buddhist doctrine and ritual. The dissertation also includes a Tibetan edition and an annotated English translation of the Dvitīyakrama.