Riders of the Purple Sage is a 1918 American silent Western film directed by Frank Lloyd and starring William Farnum, Mary Mersch, and William Scott. The film is about a former Texas Ranger who goes after a group of Mormons who have abducted his married sister. This Frank Lloyd silent film was the first of five film adaptations of Zane Grey's 1912 novel.

William Farnum was an American actor. He was a star of American silent cinema, and he became one of the highest-paid actors during this time.