You've Most Likely Seen Him In ...
... Darren Aronofsky's dance horror psychodrama, Black Swan. Cassel's role as the sketchy ballet instructor forever doubting Natalie Portman's character's ability to play the black swan is fairly emblematic of the roles he's played since breaking into American films a decade or so ago. He's creepy, sexy, vaguely threatening, but ambiguous enough to make you doubt yourself.

Unless You've Really Been Paying Attention, in Which Case You Remember Him From ...
... a couple of star-studded auteurist efforts. Cassel was cast as the villain in the Soderbergh sequel Ocean's Twelve, where the Parisian actor was a central part of the film's very French flair. In 2011, Cassel was in David Cronenberg's A Dangerous Method, alongside Michael Fassbender, Viggo Mortensen, and Keira Knightley.

"Wait, So He's That Guy From ..."
...basically any movie that needed a European villain to menace an A-List heroine. Hey, the man plays one heck of a bad guy. It's no surprise that he's been cast as a threatening presence towards Naomi Watts (in Eastern Promises), Nicole Kidman (in Birthday Girl), and Jennifer Aniston (in Derailed).

You Can Also Go Back and Spot Him In ...
...a trip of late-90s movies who needed authentic French character actors. In Jefferson in Paris, Cassel was, well, in Paris. The 1999 historical double of Elizabeth and The Messenger: The Story of Joan of Arc also served as Cassel's gateway from France to more American-friendly productions.

Perhaps Your Cultural Tastes Extend Beyond English-Language Movies, In Which Case...
...Cassel is probably way more familiar to you than most people. He made his breakthrough with the Cannes-winning French drama La Haine, playing an angry young man clashing with police in Paris. He also co-starred EIGHT times with his eventual wife, actress Monica Bellucci, including L'Appartement, Brotherhood of the Wolf, and the controversial rape-and-revenge drama from Gaspar Noe, Irreversible.

You Can Find Him Now In ...
...Danny Boyle's psychological thriller Trance, which once again has Cassel playing a sexy villain who may end up being something more. He's well within his wheelhouse.