Relentless is a 1948 American Western film directed by George Sherman and starring Robert Young and Marguerite Chapman in the main roles. The film was based on the story, "Three Were Thoroughbreds," by Kenneth Perkins, originally published in the June 1938 issue of Blue Book and then as a hardcover novel in 1939. IMDb and other sources mistakenly claim that the film was remade as the 1953 Audie Murphy film Tumbleweed, which was based on a similarly named story, "Three Were Renegades," by Perkins (originally published in the December 1938 issue of Blue Book). The later story, "Three Were Renegades," was published as a sort-of sequel to the earlier story, "Three Were Thoroughbreds," and the plotlines of the two films mirror the plotlines of their respective source stories.