K9 or K-9 most commonly refers to: * K9, the nickname of police dogs and the police dog unit itself * Canine or ''Canis'', a genus including dogs, wolves, coyotes, and jackals * K9 Thunder, a 155mm self-propelled artillery used by the Republic of Korea Armed Forces K9 or K-9 may also refer to:

Fictional dogs

* K9 (Doctor Who), K9 (''Doctor Who''), the name of several robotic canines in the British science fiction television series ''Doctor Who'' * K-9 (Looney Tunes), K-9 (''Looney Tunes''), a dog in the ''Looney Tunes'' cartoon series * K9 Murphy, a mechanical dog in the Japanese television series ''Tokusou Sentai Dekaranger''

Computing

* AMD K9, a microprocessor * K-9 Mail, a mail client for the Android operating system * K9 Web Protection, a web content control software * K9Copy, a DVD backup and authoring program for Unix-like operating systems

Entertainment

* K-9 (film), ''K-9'' (film), a 1989 American film ** K-9 (film series), ''K-9'' (film series), a film series consisting of four movies * K-9 (TV series), ''K-9'' (TV series) a British/Australian comedy/adventure series starring the same character as featured in ''Doctor Who'' * K9, a television station serving Boise, Idaho, now known as KNIN-TV * Sonata in G for Keyboard and Violin, K. 9, a Violin Sonatas, KV 6–9 (Mozart)#Sonata in G for Keyboard and Violin, K. 9, sonata by Wolfgang Amadeus Mozart

Military

* HMAS K9, HMAS ''K9'', an Australian submarine * K-9 (missile), a Soviet short-range air-to-air missile * Kahr K9, a variant of the Kahr K series, a 9×19mm Parabellum semi-automatic pistol manufactured by the American company Kahr Arms * K9 Thunder, a South Korean self-propelled howitzer * Pusan East (K-9) Air Base, an abandoned air base in Busan, South Korea

Automotive

* Kia K9, a full-size luxury sedan * K-9 (Kansas highway), a state highway in Kansas, US * BYD K9, a battery electric bus

Other