Ancient Indian treatises of a religious-philosophical nature. They are part of the Vedas and reveal the secret philosophical meaning of the Vedic hymns. They refer to the sacred writings of Hinduism of the category of shruti.

(Sanskrit "upa" - near, "ni" - at the bottom, "shad" - sit). Literally means "sitting down near" the Guru in order to receive instructions.

They discuss the philosophy, meditation and nature of God, the foundations of the philosophy of Hinduism - the concept of Brahman, the individual soul of the Atman or jiva, Paramatman and the Supreme God in His personal form of Bhagavan or Ishvara. The central theme of the Upanishads is the knowledge of the person himself and the world around him, they mainly discuss the philosophy, meditation and nature of God. It is believed that in the Upanishads the basic essence of the Vedas is stated - therefore they are also called "Vedanta" (the end, the conclusion of the Vedas). The oldest of the Upanishads, such as “Brihadaranyaka-upanisad” and “Chandogya-upanishad”, are referred to the VIII century BC whereas most others, according to scientists, emerged from VII to III century BC, while most of them appeared only in the Middle Ages.

The 10 most authoritative Upanishads are revered by all Hindus. Also, a list of the 108 Upanishads of the Advaita school, known as the Muktika, is widely known. It includes the 10 "main" Upanishads, the 21 associative Upanishads, the 23 sannyasa Upanishads, the 9 shaktas, 13 Vaishnavas, 14 shayva and 17 yoga Upanishads. In addition, there are many more texts, also called Upanishads. All of them are written at different times and belong to different trends of Hindu religious schools. Their exact number is unknown - according to some sources, it exceeds 300 names.