Robert Collier (April 19, 1885 in St. Louis, Missouri – January 9, 1950) was an American author of self-help and New Thought metaphysical books in the 20th century. He was the nephew of Peter Fenelon Collier, founder of Collier's Weekly. He was involved in writing, editing, and research for most of his life. His book The Secret of the Ages (1926) sold over 300,000 copies during his life. Collier wrote about the practical psychology of abundance, desire, faith, visualization, confident action, and personal development.