The book presents an edition, English translation and study of the Dharma Pātañjala, a previously unpublished Old Javanese-Sanskrit Śaiva scripture transmitted through a single palm-leaf codex of West Javanese origin dating back to the 15th century AD. The cultural and doctrinal background of the text, as well as its codicological and philological aspects, are introduced in Part I. Part II presents an annotated diplomatic edition of the text with facsimile reproductions of the codex on facing pages, followed by a critical edition with English annotated translation. Part III is a systematic study focusing on the interpretation of the doctrines taught in the Dharma Pātañjala in comparison with related Sanskrit texts from the Indian Subcontinent and Old Javanese scriptures from the Indonesian Archipelago. The Dharma Pātañjala is doubly important: first, because it has been preserved on a codex belonging to a rare tradition of manuscripts from Java, which is significantly older than the majority of Balinese manuscripts containing Old Javanese texts; and second, because it documents an early tradition of speculative texts (Tattva), which was previously known to us only through two Old Javanese scriptures, namely the Vṛhaspatitattva and the Tattvajñāna. e Dharma Pātañjala thus fills a gap in our knowledge of Śaiva theology and philosophy in pre-Islamic Indonesia, and also casts light on the origin and development of Śaivism in the Indian Subcontinent. The author of the Dharma Pātañjala adopted a variety of Pātañjala yoga (aṣṭāṅgayoga) instead of the Śaiva (ṣaḍaṅga) yoga that is common in other Old Javanese texts, and attuned it to a Śaiva doctrinal framework. When elaborating his syncretic system, the author seemingly followed a hitherto unknown commentarial tradition to the Sanskrit Yogasūtra that is related, albeit by no means identical, to that of the Yogasūtrabhāṣya. The Dharma Pātañjala also documents a variety of non-dualist Śaivism that may be regarded as early Saiddhāntika in nature, but in which more archaic, pre-Saiddhāntika (i.e. Pāśupata) elements have been retained as doctrinal ‘fossils’.