William Quan Judge was an Irish-American mystic, esotericist, and occultist, and one of the founders of the original Theosophical Society. He was born in Dublin, Ireland. When he was 13 years old, his family emigrated to the United States. He became a naturalized citizen of the US at age 21 and passed the New York state bar exam, specializing in commercial law.

The Theosophical Society is the organizational body of Theosophy, an esoteric new religious movement. It was founded in New York City, U.S. in 1875. Among its founders were Helena Blavatsky, a Russian mystic and the principal thinker of the Theosophy movement, and Henry Steel Olcott, the society's first president. It draws upon a wide array of influences among them older European philosophies and movements such as Neoplatonism and occultism, as well as parts of Asian religious traditions such as Hinduism, Buddhism, and Islam.