K-9 is a 1989 American buddy cop action comedy film starring Jim Belushi and Mel Harris. It was directed by Rod Daniel, written by Steven Siegel and Scott Myers, produced by Lawrence Gordon and Charles Gordon, and released by Universal Pictures.

Belushi plays bad-tempered San Diego police detective Michael Dooley, who has been tagged for execution by a major international drug dealer named Ken Lyman (played by Kevin Tighe). To help, K-9 Sergeant Brannigan (played by Ed O'Neill) gives Dooley an unorthodox drug-sniffing police dog called "Jerry Lee" (named after rock-and-roll singer Jerry Lee Lewis). The duo attempt to put Lyman behind bars but Dooley quickly learns Jerry Lee is a mischievous smart aleck who works only when and how he wants to. Many of the film's gags revolve around Jerry Lee's playfully destructive episodes.

The film was followed by a K-9 film series, including two direct-to-video sequels, K-911 (1999) and K-9: P.I. (2002); as well as a television spin-off film titled K-9000, that was intended to be the pilot episode to a TV series that was not ordered.