The Unified Rules of Mixed Martial Arts are the regulatory backbone of nearly every sanctioned MMA contest in North America and the majority of major promotions worldwide. They were drafted and first adopted by the New Jersey State Athletic Control Board (NJSACB) in April 2001, then ratified by the Association of Boxing Commissions (ABC) so that fighters, promoters and referees could move between jurisdictions without relearning the sport. Before 2001, MMA in the United States operated under a patchwork of "no holds barred" rulesets that varied by event; the Unified Rules gave the sport a single legal vocabulary and is what eventually allowed the UFC, Bellator and most regional shows to be sanctioned by state commissions.
The rules were significantly revised in 2017 to address recurring scoring confusion and to redefine what counts as a "grounded" opponent. That update is the version most modern commissions enforce today, although small regional differences remain.
Legal vs illegal techniques
Almost all striking with fists, feet, knees and elbows is legal, along with takedowns, throws, clinch work, ground-and-pound and submissions. The list of fouls, however, is long and strictly enforced. The most commonly cited illegal techniques are: strikes to the back of the head (the "mohawk" line), eye pokes, fish-hooking, groin strikes, biting, hair-pulling, head-butts, small-joint manipulation (grabbing individual fingers or toes), strikes to the spine or kidneys with a downward elbow, throat strikes, clawing or pinching, throwing an opponent on their head or neck (the "piledriver"), grabbing the cage or shorts, and timidity (refusing to engage or intentionally spitting out the mouthpiece).
Two prohibited techniques are worth singling out. The first is the "12-to-6" elbow — an elbow strike thrown straight down from the 12 o'clock position to the 6 o'clock position. Its ban is a historical artefact rather than a medical one; the rule originates from a 2001 NJSACB hearing where commissioners associated the motion with karate demonstrations of breaking bricks and concluded, without strong evidence, that it was uniquely dangerous. Most coaches and even the ABC's own committees have argued for years that the rule should be removed, and several promotions and commissions are now moving in that direction.
The second is knees and kicks to a grounded opponent's head. Pre-2017, a fighter was considered "grounded" if any part of the body other than the soles of the feet touched the canvas — meaning a single fingertip on the mat made head-kicks and knees illegal. The 2017 update changed the definition: a fighter is now grounded only if both palms (or fists), or any other body part beyond the feet, are actually on the canvas. A fighter who places only fingertips down is no longer considered grounded under the updated rule, although several commissions (notably California's CSAC for a period) declined to adopt this change immediately.
How rounds work
Non-title fights are three rounds of five minutes with one-minute rest periods. Championship fights and selected main events are five rounds of five minutes. Amateur MMA typically uses three rounds of three minutes.
How a fight ends
A bout can end by knockout (KO) when a fighter is rendered unconscious by a legal strike; technical knockout (TKO) when the referee, ringside physician or a corner stops the fight because a fighter can no longer intelligently defend themselves; submission, either by tap-out, verbal submission or technical submission (the referee stops the bout because a choke has rendered the fighter unconscious or a joint is at imminent risk); judges' decision after the final round (unanimous, split or majority); disqualification (DQ) for repeated or flagrant fouls; technical decision when an accidental foul ends the bout after the halfway point; technical draw under similar circumstances before the halfway point; and no contest, typically when an accidental foul ends a fight too early to score or when post-fight testing invalidates a result.
Regional variations
The Unified Rules are the baseline, but small differences persist. The Nevada State Athletic Commission (NSAC) and CSAC interpret the grounded-opponent rule slightly differently in practice. British Columbia and several Canadian provinces enforce stricter elbow restrictions. The United Kingdom, which has no national commission, allows promotions to adopt their own variants — most reputable UK shows mirror the Unified Rules, but soccer kicks and stomps to a grounded opponent (banned under Unified) are legal in a handful of international rulesets such as ONE Championship and some Japanese events. Always check the host commission's specific bulletin before a fight; what is legal in Las Vegas is not necessarily legal in Vancouver.