The Kybalion (full title: The Kybalion: A Study of the Hermetic Philosophy of Ancient Egypt and Greece) is a book originally published in 1908 by "Three Initiates" (often identified as the New Thought pioneer William Walker Atkinson, 1862–1932) that purports to convey the teachings of Hermes Trismegistus.

While it shares with ancient and medieval Hermetic texts a number of traits such as philosophical mentalism, the concept of 'as above, so below', and the idea that everything consists of gendered polar opposites, as a whole it is more indebted to the ideas of modern occultist authors, especially those of the New Thought movement to which Atkinson belonged. A modern Hermetic tract, it has been widely influential in New Age circles since the twentieth century.

The title Kybalion looks like an ancient Greek word, but it has no known meaning in that language. It was likely made up in an attempt to convey a false sense of antiquity.

A central concept in the book is that there are "seven Hermetic principles, upon which the entire Hermetic philosophy is based". These are, as literally quoted from the book:

1. The principle of mentalism

"The All is Mind; the Universe is Mental."

2. The principle of correspondence

"As above, so below; as below, so above.” [...] This principle embodies the truth that there is always a correspondence between the laws and phenomena of the various planes of being and life.