Isis Unveiled: A Master-Key to the Mysteries of Ancient and Modern Science and Theology, published in 1877, is a book of esoteric philosophy and Helena Petrovna Blavatsky's first major work and a key text in her Theosophical movement.

Helena Petrovna Blavatsky, often known as Madame Blavatsky, was a Russian and American mystic and author who co-founded the Theosophical Society in 1875. She gained an international following as the leading theoretician of Theosophy.