Third eye
The third eye (also called the mind's eye or inner eye) is a mystical invisible eye, usually depicted as located on the forehead, which provides perception beyond ordinary sight. In Hinduism, the third eye refers to the ajna (or brow) chakra. In both Hinduism and Buddhism, the third eye is said to be located around the middle of the forehead, slightly above the junction of the eyebrows, representing the enlightenment one achieves through meditation.
Especially in Eastern spiritual practices, the third eye refers to the gate that leads to the inner realms and spaces of higher consciousness, and often symbolizes a state of enlightenment. The third eye is often associated with religious visions, clairvoyance, the ability to observe chakras and auras, precognition, and out-of-body experiences.

In Hinduism
In Hinduism, the third eye refers to the ajna (or brow) chakra, said to be located around the middle of the forehead, slightly above the junction of the eyebrows. Hindus place a "tilaka" between the eyebrows as a representation of the third eye, which is also seen on expressions of Shiva. He is referred to as "Tryambaka Deva", or the three-eyed lord, where his third eye symbolizes the power of knowledge, and the detection of evil. His eye is depicted by three horizontal lines in the middle of his forehead.

In Buddhism
In Buddhism, the third eye is said to be located around the middle of the forehead, slightly above the junction of the eyebrows, Buddhists regard the third eye as the "eye of consciousness", representing the vantage point from which enlightenment beyond one's physical sight is achieved, and use an urna to the same effect as Hindus.  The third eye, or the “Eye of Wisdom”, is discerned on the deity Buddha.

In Taoism
In Taoism, third eye training involves focusing attention on the point between the eyebrows with the eyes closed, and while the body is in various qigong postures. The goal of this training is to allow students to tune into the correct "vibration" of the universe and gain a solid foundation on which to reach a more advanced meditative state. Taoism teaches that the third eye, also called the mind's eye, is situated between the two physical eyes, and expands up to the middle of the forehead when opened. Taoism asserts that the third eye is one of the main energy centers of the body located at the sixth Chakra, forming a part of the main meridian, the line separating left and right hemispheres of the body.

In Theosophy
Adherents of theosophist H. P. Blavatsky have suggested that the third eye is in fact the partially dormant pineal gland, which resides between the two hemispheres of the brain. Reptiles and amphibians sense light via a third parietal eye—a structure associated with the pineal gland—which serves to regulate their circadian rhythms, and for navigation, as it can sense the polarization of light. She states that certain functions of the mind are associated with the pineal gland and the acervulus cerebri was absent in children below the age of six. C. W. Leadbeater thought that by extending an "etheric tube" from the third eye, it is possible to develop microscopic and telescopic vision. It has been asserted by Stephen Phillips that the third eye's microscopic vision is capable of observing objects as small as quarks. According to this belief, humans had in far ancient times an actual third eye in the back of the head with a physical and spiritual function. Over time, as humans evolved, this eye atrophied and sunk into what today is known as the pineal gland. Rick Strassman has hypothesized that the pineal gland, which maintains light sensitivity, is responsible for the production and release of DMT (dimethyltryptamine), an entheogen which he believes could be excreted in large quantities at the moments of birth and death.

See also
Body of light – Hermetic starfire body
Consciousness – Awareness of internal and external existence
Erlang Shen – Deity in the Chinese / Buddhist pantheon
Eye of Horus – Ancient Egyptian symbol of protection, royal power and good health
Eye of Providence – Symbol of all-seeing eye (usually shown in triangle and/or surrounded by rays)
History of the pineal gland – Scientific research on the pineal gland as the third eye
Occult – Knowledge of the hidden or the paranormal
Parietal eye – Part of the epithalamus

References
Citations
Works cited
Blavatsky, H. P. (1893). The Secret Doctrine. Vol. 2. London: Theosophical Publishing House.
Cavendish, Richard, ed. (1994). Man, Myth and Magic. Vol. 19. New York: Marshall Cavendish. ISBN 978-0839360353.
Dennett, Daniel C. (1991). Consciousness Explained. Boston: Little, Brown and Company. ISBN 0-316-18065-3.
Dhillon, Neeru; Singh, Arun D.; Dua, Harminder S. (February 1, 2009). "Lord Shiva's third eye". British Journal of Ophthalmology. 93 (2): 136. ISSN 0007-1161. PMID 19174398.
Jefferson, R. B. (1982). The Doctrine of the Elixir. Coombe Springs Press. ISBN 978-0900306150.
Leadbeater, C. W. (1994) [1927]. The Chakras. Wheaton, IL: Theosophical Publishing House.
Phillips, Stephen (1980). Extrasensory Perception of Quarks. Wheaton, IL: Theosophical Publishing House. ISBN 978-0-8356-0227-3.
Saraswati, Satyananda (2001). Kundalini Tantra. Bihar, India: Yoga I Publications Trust. ISBN 978-8185787152.
Strassman, Rick J. (2001). DMT: The Spirit Molecule. A Doctor's Revolutionary Research into the Biology of Near-Death and Mystical Experiences. Rochester, VT: Park Street. ISBN 978-0-89281-927-0.

Further reading
Gazizova, V. (2018). "From Buddhism to 'Cosmic Religion': Religious Creativity in Kalmykia". Anthropology & Archeology of Eurasia. 57 (1): 5–37. doi:10.1080/10611959.2018.1470427. S2CID 149842761.
Little, Tias (n.d.). "Meditation on the Third Eye". Shambhala.com. Retrieved 2022-12-12.
Little, Tias (2016). Yoga of the Subtle Body: A Guide to the Physical and Energetic Anatomy of Yoga. Shambhala. ISBN 978-1611801026.
Sagan, Samuel (2007). Awakening the Third Eye (3rd ed.). Roseville, N.S.W., Australia: Clairvision. ISBN 978-0-9586700-5-0.

External links

Meaning of Buddha eye - Images of Buddha Eyes
 Media related to Ajna chakra (third eye) at Wikimedia Commons