K9

K9 or K-9 may refer to:

Working dogs

K-9 (Doctor Who), the name of several robotic canines in the long-running British science fiction television series, Doctor Who
K9 Murphy, a mechanical dog in the Japanese television series Tokusou Sentai Dekaranger
K-9 (Looney Tunes), Marvin the Martian's pet Martian dog in the Looney Tunes cartoon series from Warner Bros
K-9 (Transformers)

HMAS K9, Australian submarine
K9 Thunder, 155 mm self-propelled artillery used by the Republic of Korea Armed Forces
AMD K9, microprocessors
Kahr K9, a 9x19mm Parabellum semi-automatic pistol manufactured by the American company Kahr Arms

K-9 (film), starring James Belushi
K-9 (Kansas highway), a state highway in the U.S. state of Kansas
K9 Web Protection, Web content control software
K-9 Mail, a mail client for the Android (operating system), also called k9 or k9mail
K9Copy, a DVD backup and authoring program for Unix-like OSs (GNU/Linux and BSD)
KNIN-TV, the CW affiliate in Boise, Idaho that was known as K9 in the late 1990s
K-9 (missile), a long-range air-to-air missile developed by the Soviet Union in the late 1950s
K-9 (TV series) a British/Australian comedy/adventure series starring the same character as featured in Doctor Who as listed above.