The Defector is a 1966 thriller film starring Montgomery Clift, Hardy Krüger, Roddy McDowall and Macha Méril. It was directed and co-written by Belgian director/producer Raoul Lévy and based on the 1965 novel L'espion (The Spy) by Paul Thomas.

This was Clift's final film, and he only agreed to the part so that he could prepare himself for his next role in the 1967 film Reflections in a Golden Eye (the role went to Marlon Brando). Although obviously very ill (he died less than three months after most of the shooting was completed), Clift still managed to give a convincing performance in what has been termed a very moody and somber film. This characterization is in stark contrast to the exuberance displayed by his love interest, who was played by Méril, an obviously more youthful woman.

Lévy committed suicide on December 31, 1966, less than two months after the film's American release.