Jeet Kune Do "Way of the Intercepting Fist", also Jeet Kun Do or JKD, is a martial arts system and philosophy developed by martial artist Bruce Lee. In 2004, the Bruce Lee Foundation decided to use the name Jun Fan Jeet Kune Do to refer to the martial arts system that Lee founded. "Jun Fan" was Lee's Chinese given name, so the literal translation is "Bruce Lee's Way of the Intercepting Fist." Jeet Kune Do not only advocates the combination of aspects of different styles, it also can change many of those aspects that it adopts to suit the abilities of the practitioner. Additionally, JKD advocates that any practitioner be allowed to interpret techniques for themselves, and change them for their own purposes. For example, Lee almost always chose to put his power hand in the "lead," with his weaker hand back, within this stance he used elements of Boxing, Fencing and Wing Chun.

 
Just like fencing, he labeled this position the "On Guard" position. Lee incorporated this position into his JKD as he felt it provided the best overall mobility. Lee felt that the dominant or strongest hand should be in the lead because it would perform a greater percentage of the work. Lee minimized the use of other stances except when circumstances warranted such actions. Although the On-Guard position is a good overall stance, it is by no means the only one. Lee acknowledged that there were times when other positions should be utilized. Lee felt the dynamic property of JKD was what enabled its practitioners to adapt to the constant changes and fluctuations of live combat. Lee believed that these decisions should be done within the context of "real combat" and/or "all out sparring". He believed that it was only in this environment that a person could actually deem a technique worthy of adoption.

Lee believed that martial systems should be as flexible as possible. He often used water as an analogy for describing why flexibility is a desired trait in martial arts. Water is infinitely flexible. It can be seen through, and yet at other times it can obscure things from sight. It can split and go around things, rejoining on the other side, or it can crash through things. It can erode the hardest rocks by gently lapping away at them or it can flow past the tiniest pebble. Lee believed that a martial system should have these attributes. JKD students reject traditional systems of training, fighting styles and the Confucian pedagogy used in traditional kung fu schools because of this lack of flexibility. JKD is claimed to be a dynamic concept that is forever changing, thus being extremely flexible. "Absorb what is useful; Disregard that which is useless" is an often quoted Bruce Lee maxim. JKD students are encouraged to study every form of combat possible. This is believed to expand one's knowledge of other fighting systems; to both add to one's arsenal as well as to know how to defend against such tactics.