The Secret of Dr. Kildare is a 1939 American film directed by Harold S. Bucquet and produced by Metro-Goldwyn-Mayer. This was the fourth of a total of ten Dr. Kildare pictures, Lew Ayres starred all but the first.

Dr. James Kildare is a fictional American medical doctor, originally created in the 1930s by the author Frederick Schiller Faust under the pen name Max Brand. Shortly after the character's first appearance in a magazine story, Paramount Pictures used the story and character as the basis for the 1937 film Internes Can't Take Money, starring Joel McCrea as Jimmie Kildare. Metro-Goldwyn-Mayer (MGM) subsequently acquired the rights and featured Kildare as the primary character in a series of American theatrical films in the late 1930s and early 1940s. Several of these films were co-written by Faust, who also continued to write magazine stories and novels about the character until the early 1940s. Kildare was portrayed by Lew Ayres in nine MGM films. Later films set in the same hospital featured Dr. Gillespie. Ayres returned to voice the Kildare character in an early 1950s radio series. The 1961–1966 Dr. Kildare television series made a star of Richard Chamberlain and gave birth to a comic book and comic strip based on the show. A short-lived reboot of the TV series, Young Doctor Kildare, debuted in 1972 and ran for 24 episodes.