Kazuyoshi Ishii (石井 和義, born June 10, 1953) is a Japanese master of Seidokaikan karate and founder of the K-1 fighting circuit, a widely televised international martial arts competition combining Muay Thai, karate, sanshou, taekwondo, kenpo, boxing, and kickboxing. His karate training began with Kyokushin karate, but he formed his own karate organization in 1980, began promoting televised karate competitions, and started staging K-1 events in 1993.