The Guhyasamāja Tantra (Sanskrit: Guhyasamājatantra; Tibetan: Gsang ’dus rtsa rgyud (Toh 442); Tantra of the Secret Community) is one of the most important scriptures of Esoteric Buddhism. In its fullest form, it consists of seventeen chapters, though a separate "explanatory tantra" (vyākhyātantra) known as the Later Tantra (Sanskrit: Guhyasamāja Uttaratantra; Tibetan: Rgyud phyi ma. (Toh 443)) is sometimes considered to be its eighteenth chapter. Many scholars believe that the original core of the work consisted of the first twelve chapters, with chapters thirteen to seventeen being added later as explanatory material.
In India, it was classified as a Yoga or Mahāyoga Tantra. In Tibet it is considered an Unexcelled Yoga Tantra (rnal ’byor bla med rgyud). It develops traditions found in earlier scriptures such as the Compendium of Reality (Sanskrit: Sarva-tathāgata-tattva-saṃgraha; De bzhin gshegs pa thams cad kyi de kho na nyid bsdus pa (Toh 479)) but is focused to a greater extent on the antinomian aspects characteristic of the later Buddhist Tantras. Naropa and Aryadeva considered the Compendium of Reality to be a root tantra in relation to the Guhyasamaja Tantra. The Guhyasamaja Tantra survives in Sanskrit manuscripts and in Tibetan and Chinese translation.
The Guhyasiddhi of Padmavajra, a work associated with the Guhyasamaja tradition, prescribes acting as a Saiva guru and initiating members into Shaiva Siddhanta scriptures and mandalas.
According to one tradition, the Guhyasamāja Tantra was taught for the first time by the Buddha in the form of Vajradhara to Indrabhuti the King of Oddiyana, also called King Dza.
As with most tantras, there are different traditions and transmissions. Perhaps the oldest surviving lineage is the Jñānapada Tradition (ye shes zhabs lugs), which goes back to Buddhaśrijñāna (late 8th century). The most important historically is the Ārya tradition (gsang 'dus 'phags lugs) which is based on commentaries attributed to Nāgārjuna, Āryadeva, and Candrakīrti. 'Gos Lotsawa Khug pa lhas btsas originated a transmission in Tibet, as did Marpa Lotsawa. The Sakya tradition received both transmissions. Tsongkhapa, founder of the Gelug tradition, considered the Esoteric Community to be the most important of the tantras and used the Ārya tradition as a template for interpreting all the other tantric traditions.