Informer may refer to:
- Informant, a member of a one organization who gives another organization information about the group
- Common informer, a historical concept in English law abolished in 1951
- Informant (psychiatry), a person who provides information about a psychiatric patient
- Informant (linguistics), a native speaker acting as a linguistic reference for a language being studied
- The Informer (novel), a 1925 novel by Liam O'Flaherty
- The Informers, a 1994 short story anthology
- "Informer" (song), a song by Snow from 12 Inches of Snow
In films and television:
- The Informer (1912 film), a film by D. W. Griffith
- The Informer (1929 film), a film by Arthur Robison
- The Informer (1935 film), a film by John Ford
- The Informers (1963 film)
- The Informers (2008 film)
- The Informer (1980 film), a Shaw Brothers film
- The Informer (TV series), a TV series featuring Ian Hendry