The Man They Could Not Hang is a 1939 American horror film directed by Nick Grinde from a screenplay by Karl Brown. It stars Boris Karloff as Dr. Henryk Savaard, a scientist who develops a procedure for bringing the dead back to life. When he is arrested and sentenced to be executed for murdering a young medical student who volunteered to be killed to test the procedure, Savaard vows retribution on the individuals responsible. Alongside Karloff, the film's cast includes Lorna Gray, Robert Wilcox, and Roger Pryor.

The Man They Could Not Hang is the first in a series of four similarly-themed but otherwise unrelated horror films produced by Columbia Pictures, all starring Karloff, informally known as the "Mad Doctor Cycle." It was followed by The Man with Nine Lives, Before I Hang (both 1940), and The Devil Commands (1941). A fifth, The Boogie Man Will Get You (1942), was a parody of the others.