The Yogasastra and its voluminous auto-commentary, the Svopajnavrtti, is the most comprehensive treatise on Svetambara Jainism. Written in the 12th century by the polymath Hemacandra, it was instrumental in the survival and growth of Jainism in India as well as in the spreading of Sanskrit culture within Jaina circles. Its influence extended far beyond confessional and geographical borders and it came to serve as a handbook for the Jain community in Gujarat and overseas. It is a systematic presentation of a set of ideas and practices originally belonging to the Svetambara canonical scriptures and traditions moulded into a coherent whole with the help of a long row of scholastic thinkers. Hemacandra integrates innovations of his own as well as non-Jaina elements of pan-Indian and Saiva provenance, attesting to a strong Tantric influence on mediaeval Jainism. Some of these elements came to be perpetually included within Svetambara orthopraxy and orthodoxy due to the normative status acquired by the Yogasastra. The present translation is the first of its kind in a Western language.