Colonel Henry Steel Olcott was an American military officer, journalist, lawyer, Freemason and the co-founder and first president of the Theosophical Society.

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.