Tetsuo: The Iron Man (鉄男, Tetsuo, 'iron man') is a 1989 Japanese science fiction horror film directed, written, produced, and edited by Shinya Tsukamoto. The film centers around an unnamed Japanese salaryman who wakes up to find pieces of metal sprouting from various parts of his body and becomes haunted by visions of metal-oriented sexual fantasies. As the man steadily becomes a hybrid of man and machine, he develops a connection with a victim from a hit-and-run accident, who is undergoing a similar transformation. The film is generally considered to be one of the greatest Japanese films of all time.

The film was the first feature-length film by Tsukamoto after he spent his youth creating film shorts and entering Japanese experimental theatre. Through his theatre work, he met like-minded people to perform in plays and later short films such as Kei Fujiwara and Taguchi. Filming proved to be difficult with much of the cast and crew abandoning the production with only Taguchi and Tsukamoto arriving on set to finish the film. After winning the Grand Prize at the Fantafestival in Italy, the film grew in popularity in Japan, becoming a top seller on home video for non-mainstream cinema.

Outside Japan, critics compared the film to the work of directors Sam Raimi, David Cronenberg, and David Lynch while still finding the film to be an original film that was difficult to parse. Tsukamoto directed a sequel titled Tetsuo II: Body Hammer. In 2012, Michael Brooke of Sight & Sound declared the film "remains one of the most pulverisingly effective sci-fi horror films of the past quarter of a century." In Japan, the film magazine Kinema Junpo included the film on their list of top 200 Japanese films in 2009.