Kiai (気合^?) /ˈkiː.aɪ/ is a Japanese term used in martial arts. There are numerous examples of the battle cry in other cultures: kiai is perhaps primarily a development of this. In the representation of Asian martial arts in cinema and in animated cartoons, Modern Kiai are often written by westerners in Romaji as Hi-yah!, Aiyah!, Eeee-yah!, or Hyah!. Traditional Japanese Dojo generally use single syllables beginning with a vowel. In the board game Go the term describes fighting spirit — see go terms for this use.

In martial arts, the term commonly refers to a short exhalation (not as yell) before or during a strike or technique. In bujutsu (Japanese arts of war), it is usually linked to an inner gathering of energy released in a single explosive focus of will. Students of Japanese martial arts such as aikido, karate, Kobudo, kendo or judo (or related arts such as taiko drumming) do not 'use', but rather allow, one's Ki to emanate from their center (Hara) while executing a technique. It also erroneously refers to the shout that accompanies some techniques when performing kata.^{[citation needed]}Kiaijutsu is at times thought to be the Japanese art of using kiai when performing martial arts. More accurately Kiai and Aiki co-exist in all Japanese Martial Arts.

Bruce Lee (born Lee Jun-fan; 27 November 1940 – 20 July 1973) was a Chinese AmericanHong Kong actor,martial arts instructor, philosopher, film director, film producer, screenwriter, and founder of the Jeet Kune Do martial arts movement. He is widely considered by many commentators, critics, media and other martial artists to be the most influential martial artist and pop culture icon of the 20th Century. He is often credited with changing the way Asians were presented in American films.

Lee was born in San Francisco to parents of Hong Kong heritage but was raised in Hong Kong until his late teens. Lee returned to the United States at the age of 18 to claim his U.S. citizenship and receive his higher education. It was during this time that he began teaching martial arts, which soon led to film and television roles.

His Hong Kong and Hollywood-produced films elevated the traditional Hong Kong martial arts film to a new level of popularity and acclaim, and sparked a major surge of interest in Chinese martial arts in the West in the 1970s. The direction and tone of his films changed and influenced martial arts and martial arts films in Hong Kong and the rest of the world, as well. He is noted for his roles in five feature-length films: Lo Wei's The Big Boss (1971) and Fist of Fury (1972); Way of the Dragon (1972), directed and written by Lee; Warner Brothers' Enter the Dragon (1973) and The Game of Death (1978), both directed by Robert Clouse.