This volume presents the first critical edition, along with an English translation, of the core chapters of a Sanskrit work of perhaps the thirteenth century surviving in five nineteenth-century witnesses: the Matsyendrasaṃhitā. The work is useful as a primary source for the history of yoga and the Śaiva religions: it reveals important links between the tantric cults of Kubjikā and Tripurā and early haṭhayoga. In addition, its frame-story (in chapters 1 and 55) relates a unique version of the yogin Matsyendra’s legend in which his disciple Gorakṣa is a Chola king. The edition is bracketed by a detailed introduction and by detailed notes on the constitution of the text, as well as an annotated translation.