ZST (pronounced Zest) is a Japan-based mixed martial arts promotion and sanctioning organization holding amateur and semi-professional MMA events.

ZST was conceived in efforts to accommodate fighters of puroresu MMA promotion RINGS that went defunct in February 2002.

On September 22, 2002, Takeshi Caesar, the president of Shoot Boxing Association (SBA), and Koki Hioki, representative of ZST, had a conversation after a Shoot Boxing event, and they announced that SBA would support ZST.

Punches, elbow strikes, knees and kicks are allowed to the head and body when both fighters are standing.

The positioning is not regarded for scoring as important factor and any motions including clinching and holding which impedes bouts are prohibited.