Kazuyoshi Ishii founds K-1
A Seidokaikan karate promoter set out to settle which striking art produced the best fighter, and in solving that problem wrote the rulebook nearly all modern kickboxing still uses.
Kazuyoshi Ishii ran Seidokaikan, a Kyokushin karate offshoot. In 1993 he launched K-1 to answer a promotional question with a competitive format: if a Kyokushin karateka, a Dutch kickboxer, a Thai nak muay and a savateur all fought, who wins?
The ruleset was the answer, and it is an elegant one. Keep the weapons every striking art shares — punches, kicks, knees. Remove elbows. And critically, break the clinch almost immediately, so no specialist can stall the fight in the phase they own. That single restriction is what makes K-1 rules feel the way they do: the fight is forced back to open range again and again, rewarding volume, footwork and the ability to hurt someone in a two-second exchange.
The format was the other innovation. A one-night, eight-man Grand Prix meant a champion won three fights in an evening, which rewards durability and finishing ability over point accumulation. The K in the name gestures at karate, kickboxing, kung fu and kempo; the 1 at finding a single champion among them.
Branko Cikatić won the first tournament. Over the following decade Ernesto Hoost, Peter Aerts, Semmy Schilt and Remy Bonjasky took most of the rest, and K-1 rules became the template that GLORY, ONE, Enfusion and the WAKO K-1 category all still follow.