Samuel Liddell MacGregor Mathers was one of the principal founders of the Hermetic Order of the Golden Dawn, a secret society active in Great Britain during the late 19th and early 20th centuries. This order was deeply rooted in Western esoteric traditions, drawing inspiration from Rosicrucianism and Freemasonry, and focused on the study and practice of Hermeticism, metaphysics, and magic. Mathers, along with William Robert Woodman and William Wynn Westcott, developed the Order's structure and teachings, which included a hierarchical system of initiation and a curriculum based on the Hermetic Qabalah, astrology, tarot, and geomancy.

Mathers played a crucial role in developing the rituals and curriculum, particularly for the Second Order, known as the Rosae Rubae et Aureae Crucis. He was instrumental in establishing the Order's temples, including the Isis-Urania Temple in London and the Ahathoor Temple in Paris. Following Westcott's departure, Mathers became the primary leader, though his authority was eventually challenged, leading to significant internal disputes and schisms within the Golden Dawn.

Samuel Liddell MacGregor Mathers was a key figure in the establishment of the Hermetic Order of the Golden Dawn. Alongside William Robert Woodman and William Wynn Westcott, he was a Freemason and member of the Societas Rosicruciana in Anglia. Mathers, along with Westcott, is credited with transforming the foundational Cipher Manuscripts into a functional system for the Order. The manuscripts outlined rituals and a curriculum covering Hermetic Qabalah, astrology, tarot, and alchemy. Mathers is particularly recognized for his contributions to the design of the curriculum and rituals for the Second Order, named the Rosae Rubae et Aureae Crucis (RR et AC).

After the departure of William Wynn Westcott from the Golden Dawn, S. Liddell MacGregor Mathers became the de facto leader. His leadership style and frequent absences from Britain, combined with personality clashes, led to growing dissatisfaction among members of the Second Order. Tensions escalated due to Mathers's perceived intermediary role with the Secret Chiefs and his close association with Aleister Crowley. A pivotal moment occurred when Mathers controversially overrode the London officials' decision to deny Crowley initiation into the Adeptus Minor grade, leading to a revolt by the London Adepts and ultimately Mathers's expulsion from the Order.

The Hermetic Order of the Golden Dawn, co-founded by Mathers, significantly influenced the landscape of Western occultism in the 20th century. Its teachings on ritual and magic formed the basis for many contemporary esoteric traditions, including Wicca and Thelema. The Order's structured system of initiation, its focus on Hermetic philosophy, and its exploration of magic contributed to a revival of occult studies. Despite internal conflicts and eventual schisms, the foundational work established by Mathers and his co-founders left a lasting impact on esoteric movements worldwide.