Thelema is a spiritual philosophy (referred to by some as a religion) that was developed by the early 20th century British writer and ceremonial magician, Aleister Crowley.

The word "Thelema" itself is the English transliteration of the Koine Greek noun θέλημα: "will", from the verb θέλω: to will, wish, purpose. In the New Testament as well as the works of Plato, Thelema includes the ideas of will, choice, inclination, desire, including sexual desire, and pleasure. As Crowley developed the religion he wrote widely on the topic, producing what are collectively termed the Holy Books of Thelema. He also included ideas from occultism, Yoga and both Eastern and Western mysticism, especially the Qabalah.

According to Crowley, every individual has a True Will, to be distinguished from the ordinary wants and desires of the ego. He identified the True Will of each individual with the Holy Guardian Angel, a daimon unique to each individual. The spiritual quest to find what you are meant to do and do it is also known in Thelema as the Great Work.

The True Will is defined as a person's grand destiny in life, and at other times as a moment to moment path of action that operates in perfect harmony with Nature. This Will does not spring from conscious intent, but from the interplay between the deepest Self and the entire Universe. Thelemites in touch with their True Will are said to have eliminated or bypassed their false desires, conflicts, and habits, and accessed their connection with the divine. Theoretically, at this point, the Thelemite acts in alignment with Nature, just as a stream flows downhill, with neither resistance nor "lust of result."