Bug is a 2006 psychological horror film directed by William Friedkin and written by Tracy Letts, and starring Ashley Judd, Michael Shannon, Lynn Collins, Brían F. O'Byrne, and Harry Connick Jr. Letts adapted the screenplay from his 1996 play of the same name. It follows an isolated woman living in a rural Oklahoma motel who spirals into psychosis after taking in a mysterious Gulf War veteran.

Bug debuted at the 2006 Cannes Film Festival before being purchased by Lionsgate, which released the film the following year in May 2007. The film received generally positive reviews from critics, who praised its intensity, directing, acting, and take on paranoia, but were polarized about its writing, in particular the film's ending. Friedkin and Letts collaborated again as director and writer on the 2011 film Killer Joe.