- HD 1080
- Runtime: 144m.
- Status: Released
- 1
- Languages: ko
- Country: South Korea
- Director: Kim Jee-woon
- Stars: Lee Byung-hun, Choi Min-sik, Jeon Kuk-hwan, Cheon Ho-jin, Oh San-ha
- keywords: psychopath, cemetery, police chief, secret agent, revenge, murder, serial killer, mercilessness, severed head, brutality, cannibal, tracking device, south korea, sadistic killer
- Production_studio: Softbank Ventures, Peppermint & Company, Siz Entertainment, Finecut, Michigan Venture Capital, Showbox, CJ Venture Investment
- Slogan: Abandon all compassion.
- providers: Amazon Prime Video, Peacock Premium, Amazon Prime Video with Ads, Peacock Premium Plus
- The I Saw the Devil is featured in the top rankings of 2010
- #4 in Top Thriller Movies of 2010
- #3 in Top Horror Movies of 2010
Kyung-chul is a dangerous psychopath who kills for pleasure. Soo-hyeon, a top-secret agent, decides to track down the murderer himself. He promises himself that he will do everything in his power to take vengeance against the killer, even if it means that he must become a monster himself.