The Mysterious Rider is a 1938 American Western film directed by Lesley Selander and starring Douglass Dumbrille, Sidney Toler, and Russell Hayden.

In the Arizona desert in the late 1800s, famed outlaw Pecos Bill (Douglass Dumbrille) and his sidekick Frosty Kilburn (Sidney Toler) hold up a stagecoach.

Having lived an outlaw life for the past twenty years, and still wanted for a murder he did not commit, Pecos Bill, whose real name is Ben Wade, decides to return to his home town disguised as a regular cowboy to see his now grown daughter.

Seeing the runaway carriage, the gallant ranch forman Wils Moore (Russell Hayden) chases them down and stops the horses.

With the help of Frosty and Wils—one of the few honest men at the ranch—Ben intends to put a stop to the cattle rustling and restore the ranch to his daughter, the rightful owner.

Knowing that Wils is on the right side of the law, Ben reveals his true identity and the truth behind how he lost his ranch—that he left his foreman William Bellounds to look after things, but he stole the ranch for himself, and now is rustling his own cattle for profit.

When Bellounds figures out that Pecos Bill is in fact Ben Wade, his former boss, he reveals his discovery to the leader of the rustlers, Cap Folsom.