Fantômas se déchaîne (French pronunciation: [fɑ̃tomas sə deʃɛn], "Fantomas Unleashed") is a 1965 film starring Jean Marais as the arch villain Fantômas opposite Louis de Funès as the earnest but outclassed commissaire Juve and the journalist Fandor, also played by Marais.

In the second film of the trilogy Fantômas kidnaps distinguished scientist professor Marchand with the aim to develop a super weapon that will enable him to menace the world.

Journalist Fandor develops an ingenious scheme whereby he disguises himself as Lefebvre and attends a scientific conference in Rome, Italy to lure Fantômas into attempting to kidnap him.

Yet, once again Fantômas escapes in style, using his Citroën DS with retractable wings that converts into an airplane in what amounts to one of the most unexpected and spectacular scenes of the genre.

It was the sixth most popular film of 1965 in France, after The Sucker, Goldfinger, Thunderball, Gendarme in New York and Mary Poppins and before God's Thunder and The Wise Guys.