The Lost World is a 1925 American silent fantasy giant monster adventure film, directed by Harry O. Hoyt and written by Marion Fairfax, adapted from Arthur Conan Doyle's 1912 novel of the same name.

Produced and distributed by First National Pictures, a major Hollywood studio at the time, the film stars Wallace Beery as Professor Challenger and features pioneering stop motion special effects by Willis O'Brien, a forerunner of his work on King Kong (1933). Doyle appears in a frontispiece to the film, absent from some extant prints.

In 1998, The Lost World was deemed "culturally, historically or aesthetically significant" by the Library of Congress and selected for preservation in the United States National Film Registry. Due to its age, the film is now in the public domain.