This dissertation recovers a largely forgotten mystical socialist movement at the turn of the twentieth century, which brought “New Age” religion into the center of the anarchist, socialist and women’s rights movements. This research also demonstrates that there exists a long-maligned but distinct religio-political tradition that Joslyn calls the “New Age left.” This tradition first became an important element of the American left at the turn-of-the-century and then came to influence the mid-twentieth-century “cultural left” and “new left.” Its contemporary resonances include the 2020 ill-fated presidential run of “New Age” guru and democratic-socialism-supporter Marianne Williamson.