Infection (感染, Kansen) is a 2004 Japanese horror film directed by Masayuki Ochiai. The film is about a run-down hospital where a doctor's mistake unwittingly creates horrific consequences for the staff at the hospital. The film was adapted from Ochiai's earlier screenplay from Tales of the Unusual. On its release, the film was part of the six-volume J-Horror Theater series.

On the film's release in Japan, it was the second highest gross film at the weekend box office, only being beaten by the film I Robot.