Filth is a 2013 psychological black comedy crime thriller film written and directed by Jon S. Baird, based on Irvine Welsh's 1998 novel Filth. The film was released on 27 September 2013 in Scotland, 4 October 2013 elsewhere in the United Kingdom and in Ireland, and on 30 May 2014 in the United States. It stars James McAvoy, Jamie Bell, and Jim Broadbent.

Irvine Welsh is a Scottish novelist and short story writer. His 1993 novel Trainspotting was made into a film of the same name. He has also written plays and screenplays, and directed several short films.