Hevajra Tantra stands out as a specimen of Vajrayanic theory and praxis from among the vast volume of Tantric Literature. It is also considered to be one of the most prominent Yogini Tantra belonging to the Anuttarayogo class of Buddhist tantras. It was one of the chief tantric cycles introduced in the later part of the 10th century A.D.

Etymology of Hevajra Tantra
"Hevajra" is composed of two syllables: "he" signifying Karuna or compassion and "vajra" signifying Prajna or wisdom. Thus the term "Hevajra" indicates the ultimate reality, which is the fusion of Sunyata and Karuna. The title also indicates the method that this tantra employs to attain its goal, which is one of Wisdom and Means. Muktavali states that Mahakaruna, with Sarvadharma Sunyata as its content, is Hevajra.

Concept of Hevajra Tantra
The method consists in uniting Prajna and Karuna, and this union of voidness and compassion results in Bodhicitta. Prajna is of the nature of the female deity and Karuna is of the nature of the male deity. The goal of tantric realization is iconographically depicted in the sexual union of the two deities. In the actual tantric praxis, the yogi becomes the male deity (Hevajra) and the Yogini is the female deity (Nairatmya) and the realization is attained through their physical union.

The term "Hevajra" taken as a whole, is the name of the principal deity of the Hevajra Sadhana. The principal deity in the Hevajra Mandala is "Heruka". There is no real distinction between Heruka and Hevajra. Heruka is worshipped singly or in union with his Prajna. When he is in "yabyum" or union he is generally known as Hevajra. By being in union with his Prajna (Vajravarahi/Nairatmya) he embodies in himself the method of this Non-Dual Tantra.

Features of Hevajra Tantra
As regards the term "tantra" the Yogaratnamala says, that it is a treatise consisting of three facets, namely:

i. The Source Facet (Hetu Tantra): The Source (hetu) consists of the beings that belong to the vajra family. In the Hevajra Tantra, the members of the Vajra are the characters in the drama of the Lord Buddha (buddhanataka). Their dialogue is the vehicle through which the nature of and the means to the enlightened states of the Buddha is revealed.

ii. The Fruit Facet (Phala-Tantra): The Fruit (phala) is the perfected Hevajra, that is, Vajradhara in the form of Hevajra.

iii. The Means Facet (Upaya-Tantra): The Means (upaya) are the methods of practice which are described in the Hevajra Tantra.

The theories of Hevajra Tantra consist of the notions of Sunyata and Karuna and the production of Bodhicitta. The praxis comprises of the visualization of the deities of the Hevajra Mandala and the Sadhana. The principal deity, the method, as well as the treatise itself are known by the same name, Hevajra.

Texts of Hevajra Tantra
The Hevajra Tantra has Chinese, Tibetan, Sanskrit, Japanese and English versions, all of which have been published. The Sanskrit original of this tantra consists of 750 slokas in two parts. However, "Vajragarbha", probably the first commentator on the text, states in his introduction that it is but a shorter version of the original work, which had 32 parts and 500,000 slokas. The Chinese translation repeats a similar tradition, explaining that the work has two sections from an original of 31.

The text of the Hevajra Tantra that is available now consists of 23 chapters divided into two parts. The part one consists of 11 chapters and the part two consists of 12 chapters. The treatise is composed of discourses that ensue between Bhagavan (Buddha as Vajradhara) and his disciple Vajragarbha. In the second part, the discourses between Bhagavan and his consort as well are found. These discourses convey the theory, practice, and experience of the karma, the processes of the Buddhist tantric method. The commentaries, Yogaratnamala and Muktavali which accompany the text, explain the relevant terms and phrases of the text. It is stated at the beginning that Buddha is in a state of sexual union with his "diamond women". It is in this state that he explains the various processes of the tantra and the nature of Enlightened Consciousness.

The Hevajra Tantra must be viewed in the larger context of the concepts and practices from various religious and social contexts that are found in Vajrayana. Monastic ideals of Hinayana and Mahayana Buddhism also find their way into this tantra. Views and methods found in the Guhyasamaja Tantra and the Sarvatathagata Tattvasamgraha have deeply influenced the formation of this treatise.