Russian Authentism (Russian: Аутентизм), incorporated as the Thesaurus Non-Confessional Spiritual Union (Внеконфессиональный Духовный Союз "Тезаурус"), is a Rodnover (Slavic Neopagan) philosophy and psychological practice originally founded in 1984 by Sergey Petrovich Semyonov (b. 1952) in Saint Petersburg. Semyonov also termed his doctrine Russian Vedism (Русский Ведизм), a name shared by many other currents within Rodnovery. The adherents of the philosophical doctrine are called Authentists, while the core members of the Thesaurus Union are called Thesaurites. The philosophy and practice of the movement are considered as a way to lead humanity to the realisation of its divine nature, its intimate connection with—and even identity with—God.

Russian Authentism was founded in 1984 by the medical doctor, psychologist and psychotherapist Sergey Petrovich Semyonov, who was born in Saint Petersburg in 1952, and graduated in 1976 at the First Pavlov State Medical University of St. Petersburg, then First Medical Institute of Leningrad. During his medical practice, he became convinced that most chronic diseases are the outcome of wrong lifestyles; therefore, he dedicated himself to the promotion of wellness practices. He gathered a group of acolytes and they studied Eastern religious and health techniques such as vegetarianism, yoga, the thought of Sri Aurobindo, and others. They came to the conclusion that there is no universal healthy lifestyle, since people differ significantly from each other. In the early 1980s, Semyonov discovered the fundamental principle of the need for an individual life to correspond to its own nature, which he called "authenticity". He formed a new group of acolytes with whom he explored the best methods for "authentication", that is to say the process of realisation of authenticity.

In 1984, Semyonov founded the "Studio of Psychic Culture" (Студию психической культуры), which one year later was transformed into the "Leningrad Club of Psychic Culture—World" (Ленинградский клуб психической культуры "Мир"). The organisation was engaged in the dissemination of the doctrine of Russian Authentism and published the samizdat magazines Psychic Culture (Психическая культура) and Kazan Cathedral (Казанский собор). In 1987 the organisation was dissolved by the authorities of the Soviet Union, according to Semyonov for its engagement in politics, but it continued to exist as an underground organisation. The original organisation was focused on the relationship between ethnic groups, especially Russians and Jews, and it was internally organised into the "Rus" and "Sinai" subgroups which tried to find points of intersection between Russian and Jewish cultures in order to overcome the conflict between them. In 1989 there was a split between the two groups, and Semyonov made a choice in favour of the "Rus", which eventually developed into the Thesaurus Union focused exclusively on Russian religious culture.

The ideology of Authentism is presented in a number of publicistic articles and brochures, among which the main ones may be considered Authentism – The Ideology of the Russian Revival (Аутентизм – идеология русского возрождения) and Russia. Russian Order and Russian History (Россия. Русский порядок и русская история). The religious doctrine is presented in a compilation of a cycle of lectures carried out over the years and published under the title Public Sermon of Godmanhood (Публичная проповедь Богочеловечества).

The term "Authentism" derives from the Latin word authenticus, meaning "authentic, self-made, self-consistent", "consistent with one's own true nature". The adherents prefer not to qualify Russian Authentism as a "religion", but rather as a philosophical "worldview" and a psychological practice, a system of ideas which covers everything from healthy lifestyle to all the aspects of human life. Its purpose is to lead an individual to reach the state of "authenticity", which is realised when one discovers that he is not merely a cultural being but an immortal spirit with a divine nature, a spark of God—thus, "authenticity" corresponds to the concept of "godmanhood". The alternative name of the movement, "Russian Vedism", was defined by Sergey P. Semyonov as expressing the "original experience of ascent in the spirit of the Russian people at the end of the Soviet era". Russian Authentism is institutionalised into the psychological order of the Thesaurus Union; the non-professional adepts of Authentism are known as "Authentists" (аутентисты), while the professional psychologists who are members of the Thesaurus Union are called "Thesaurites". The Latin word thesaurus, meaning "treasure", refers to the Russians as the custodians of the idea of the genealogical connection between humanity, reality and God.

The scholar Igor Popov defined Russian Authentism as a synthesis of Slavic paganism, Russian cosmism and psychoanalysis. The scholar Vadim Alekseyev defined the movement as a synthesis of "religious ideas of the East and the West with the personal religious experience of the founder", and as an "eclectic religious system" in which Slavic paganism and Semyonov's own ideas are mixed—by Semyonov's own admission—with Vladimir Solovyov's thought, Carl Jung's theory of the archetypes, Sri Aurobindo's integral yoga, and meditation techniques. Other influences in Russian Authentism are Nikolay Berdyaev, Fyodor Dostoyevsky and Pierre Teilhard de Chardin. Such versatility makes Russian Authentism appealing for a wide range of people from different backgrounds: the semblance of scientificness appeals to former atheists; elements from Eastern thought are accessible to people who already practised yoga; the concept of godmanhood is familiar to those who have an acquaintance with broader Russian religious philosophy; the "Perunic" severity and quasi-militarism of the Thesaurus Union and the political ideas of the doctrine make the movement appealing to young nationalists; lastly, the methods of health improvement are attractive for the elderly. The scholar Alexey V. Gaidukov found that Russian Authentism is a complex philosophical system applicable to different fields of thought and practice; it is "difficult for the uninitiated" and distinguished by a precisely defined attitude towards other religions. The purpose of the movement as a whole is the construction of a civilisation of godmen, through personal improvement and active participation in the transformation of society.

Russian Authentism tries to synthesise all aspects of human experience, chiefly politics, philosophy and medicine, into a single system. The aim of Russian Authentism is to reveal mankind's true spiritual essence, which is identical with God, Rod (Род, "Begetter")—which is viewed as the complementary unity of Belobog-Svetovid and Chernobog-Veles—and therefore the aim is ultimately the unity of mankind and God, a work which is the mission of the Russians as carriers of the idea of God opposed to Western materialism and individualism.

All the gods exist within the supreme Rod, and articulate in complementary dualities which reflect the supreme duality of Rod itself, its two primary faces: its bright celestial facet Belobog ("White God") or Svetovid ("Lord of Holiness"), and its dark terrestrial facet Chernobog ("Black God") or Veles ("Lord of Will", according to Semyonov's etymological interpretation). The supreme God unites in itself all the natural processes of life and death, collectively represented by Belobog and Chernobog.