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Upsets are the heartbeat of combat sports. Any night can produce a result that nobody saw coming, no matter how dominant a champion appears to be. In MMA especially, where one punch or one submission can end everything in seconds, the gap between a prohibitive favorite and a significant upset is often narrower than the odds suggest. These are ten of the most shocking upsets in MMA history.

1. Matt Serra def. Georges St-Pierre (UFC 69, April 2007)

The gold standard of MMA upsets. GSP was the welterweight champion, universally regarded as the best at 170 pounds, and Serra was a +800 underdog who had won a season of The Ultimate Fighter. Less than four minutes into the fight, Serra had knocked GSP down with a right hand, followed up relentlessly, and stopped the champion. Nothing in MMA before or since better exemplifies how one punch can change everything.

2. Holly Holm def. Ronda Rousey (UFC 193, November 2015)

Ronda Rousey was arguably the most dominant champion in UFC history at that point, having finished every opponent without going to a decision. Holly Holm was a respected challenger but not considered a genuine threat. Holm outboxed Rousey for a full round and a half before landing the head kick and follow-up punches that produced the most stunning knockout in women’s MMA history. The arena at Melbourne fell silent before erupting in disbelief.

3. Chris Weidman def. Anderson Silva (UFC 162, July 2013)

Silva had been the UFC’s pound-for-pound king for six years, defending the middleweight title ten consecutive times. Weidman was a talented contender but had no business beating Anderson Silva in most pre-fight analyses. Silva appeared to be playing around in the second round, dropping his hands and inviting Weidman’s punches, when Weidman connected and ended the dynasty. The result opened a debate about whether Silva’s showboating cost him the fight, but the result stands.

4. Sean O’Malley def. Petr Yan (UFC 280, October 2022)

Yan was a former bantamweight champion considered far too technical and experienced for O’Malley, who was seen as flashy but unproven against elite opposition. O’Malley’s left hand caught Yan in the third round for a highlight-reel knockout that announced him as a legitimate title contender. He would go on to win the championship shortly after.

5. Ryan Bader def. Fedor Emelianenko (Bellator 214, January 2019)

Fedor is considered the greatest heavyweight in MMA history. Bader had power and wrestling. The Bellator Heavyweight Grand Prix semifinal lasted 35 seconds: Bader landed two right hands that dropped Fedor, followed up immediately, and the stoppage came. For fans who had watched Fedor dominate an era, the result was incomprehensible. The Bellator arena went quiet in disbelief.

6. Frank Mir def. Brock Lesnar (UFC 81, February 2008)

Lesnar arrived from WWE/pro wrestling as a massive physical specimen with legitimate NCAA wrestling credentials. He dominated Mir for two minutes, landing strikes and overwhelming him with size. Then Mir caught him in a kneebar from the bottom and forced a tap. For a man making just his second MMA appearance, Lesnar was widely expected to bowl Mir over. The submission finish was a reminder that in MMA, no position is safe from a submission specialist.

7. Sean Strickland def. Israel Adesanya (UFC 293, September 2023)

Strickland had improved significantly but was still a significant underdog against Adesanya, the two-time middleweight champion widely considered among the division’s all-time greats. Strickland’s relentless pressure, high output, and willingness to take Adesanya’s counters in order to land more volume earned him a unanimous decision. It was one of the year’s biggest upsets across all of combat sports.

8. Conor McGregor def. Jose Aldo (UFC 194, December 2015)

Aldo was a ten-year unbeaten champion. McGregor was exciting and compelling but had never fought at the championship’s level before. The 13-second knockout that ended Aldo’s dynasty is technically an upset because Aldo was the established champion and McGregor had never been in a UFC title fight. It was also one of the greatest moments in the sport’s history, a single strike erasing a decade of dominance in less time than it takes to read this sentence.

9. Stipe Miocic def. Francis Ngannou (UFC 220, January 2018)

Ngannou had been knocking out everyone in front of him with the hardest recorded punch force in human history. He was the clear betting favorite and seemed like an unstoppable force of nature. Miocic survived the early power with smart footwork and level changes, took the fight to the ground, and dominated with wrestling and ground-and-pound across five rounds. The champion had stopped the monster.

10. Justin Gaethje def. Tony Ferguson (UFC 249, May 2020)

Ferguson had won 12 consecutive fights and was considered one of the most formidable challengers in lightweight history. His unorthodox style had beaten top contenders for years. Gaethje landed leg kicks relentlessly throughout the fight, destroying Ferguson’s mobility, and finished with strikes in the fifth round. The performance exposed something no one expected to see: Tony Ferguson, apparently beaten.

These moments are part of why MMA endures as a spectator sport. The next upset is always one punch, one sub, one kick away. That uncertainty is not a flaw in the sport — it is the sport’s greatest feature.