U-Kei (U系 or ユーけい, eng. U-Series, U-Group or Class U）is a combat sports related term that refers to either a professional wrestling-, martial arts- and/or mixed martial arts organization, programme or a sportsman with either UWF and/or shootwrestling roots.
The U refers to Japanese professional wrestling promotion UWF, that was active from 1984 to 1986. UWF is credited in pioneer in the "shoot-style" of pro-wrestling and has acted as genesis to modern mixed martial arts, in both Japan and overseas.[1] [2] [3]
During early days of shoot-style pro wrestling in Japan, the professional wrestling and/or mixed martial arts organizations that derived from the idea of UWF are collectively called "UWF-kei", or "U-kei" for short.[4] [5] [6]