Reuben Swinburne Clymer (November 25, 1878 - June 3, 1966) was an American occultist and modern Rosicrucian responsible for either reviving or creating the Fraternitas Rosae Crucis, perhaps the oldest continuing Rosicrucian organization in the Americas. He practiced alternative medicine, and wrote and published works on it as well as (his version of) the teachings of Paschal Beverly Randolph, sex magic, vegetarianism, religion, alchemy, and Spiritualism.