This Man Is Dangerous is a 1936 thriller novel by the British writer Peter Cheyney. It is the first in his series of ten novels featuring the FBI agent Lemmy Caution. A bestseller, it enabled Cheyney to leave his job as a policeman and become a full-time novelist.
In 1953 it was made into a French film of the same title directed by Jean Sacha and starring Eddie Constantine as Caution along with Colette Deréal, Grégoire Aslan and Claude Borelli.