KO, K.O., Ko or Kö may refer to:

• Ko (film), a Tamil action movie directed by K.V. Anand released in April 2011
• Keith Olbermann (born 1959), American broadcaster and the host of Current TV's Countdown with Keith Olbermann

A knockout (KO or K.O.) is a fight-ending, winning criterion in several full-contact combat sports, such as boxing, kickboxing, muay thai, mixed martial arts, karate, some forms of taekwondo and other sports involving striking. A full knockout is considered any legal strike or combination thereof that renders an opponent unable to continue fighting.

For Kugyo, the Buddhist monk who in 1291 assassinated Kamakura shogun Minamoto no Sanetomo, see Kugyo (Minamoto no Yoshinari)".

is the collective term for the very few most powerful men attached to the court of the Emperor of Japan in pre-Meiji eras. The kugyo was broadly divided into two groups: the , comprising the Chancellor of the Realm, the Minister of the Left, and the Minister of the Right; and the , comprising the Major Counsellor, the Middle Counsellor, the , and members of the Japanese court of the third rank or higher.

The Königsallee (, literally "King's Avenue") is an urban boulevard in Düsseldorf, state capital of North Rhine-Westphalia, Germany. The Königsallee is noted for both the landscaped canal that runs along its center, as well as for the fashion showrooms and luxury retail stores located along its sides.