This thesis contains a critical edition and annotated translation of the Khecarīvidyā of Ādinātha, an early haṭhayogic text which describes the physical practice of khecarīmudrā. 31 witnesses have been collated to establish the critical edition. The notes to the translation adduce parallels in other works and draw on Ballāla's Bṛhatkhecarīprakāśa commentary and ethnographic data to explain the text. The first introductory chapter examines the relationships between the different sources used to establish the critical edition. An analysis of the development of the text concludes that its compiler(s) took a chapter describing the vidyā (mantra) of the deity Khecarī from a larger text to form the framework for the verses describing the physical practice. At this stage the text preserved the Kaula orientation of the original work and included verses in praise of madirā, alcohol. By the time that the text achieved its greatest fame as an authority on the haṭhayogic practice of khecarīmudrā most of its Kaula features had been expunged so as not to offend orthodox practitioners of haṭhayoga and a short fourth chapter on magical herbs had been added. The second introductory chapter concerns the physical practice. It starts by examining textual evidence in the Pali canon and Sanskrit works for practices similar to the haṭhayogic khecarīmudrā before the time of composition of the Khecarīvidyā and then discusses the non-physical khecarīmudrās described in tantric works. There follows a discussion of how these different features combined in the khecarīmudrā of the Khecarīvidyā. Then a survey of descriptions of khecarīmudrā in other haṭhayogic works shows how the haṭhayogic corpus encompasses various differnt approaches to yogic practice. After an examination of the practice of khecarīmudrā in India today the chapter concludes by showing the haṭhayogic khecarīmudrā has generally been the preserve of unorthodox ascetics. In the third introductory chapter are described the 27 manuscripts used to establish the critical edition, the citations and borrowings of the text in other works, and the ethnographic sources. The appendices include a full collation of all the witnesses of the Khecarīvidyā, critical editions of chapters from the Matsyendrasaṃhitā and Haṭharatnāvalī helpful in understanding the Khecarīvidyā, and a list of all the works cited in the Bṛhatkhecarīprakāśa.