Biggest Upsets in UFC History

In mixed martial arts, the favorite doesn't always win — and our ELO rating system lets us measure exactly how shocking each result was. Every fighter carries a rating into a bout; when a heavy underdog beats a far higher-rated opponent, the gap between their two ratings at that moment is the size of the upset. The leaderboard below ranks the biggest shocks in UFC history using each fighter's real ELO on fight night — not their current or peak rating, so the numbers reflect how the fight actually looked on paper at the time. The most stunning result on record is Julianna Pena's win over Amanda Nunes at UFC 269: Oliveira vs. Poirier — a +466-point ELO swing (1,010 vs 1,476).

How We Measure UFC Upsets

Upsets are ranked by the difference between each fighter's ELO rating at the time of the fight — the rating they carried into the bout, not their current or peak rating. Because we store every fighter's pre-fight ELO, the gap you see is exactly how lopsided the matchup looked on paper that night. The winner was the underdog: their pre-fight ELO was lower than their favored opponent's, and the larger the gap, the more shocking the result.

What counts as a true upset?

Not every underdog win is a genuine upset. A fighter rated 20 or 30 points below their opponent winning is well within the noise of the sport. The results on this page are the outliers — bouts where a fighter beat someone rated hundreds of ELO points higher, often a reigning or former champion at the peak of their reign. Those are the nights that rewrite divisions and end dynasties, and ELO captures them cleanly because it already accounts for who each fighter had beaten coming in.

Why upsets matter in MMA

MMA is the most volatile of the major combat sports: four-ounce gloves, five-minute rounds, and a dozen ways to lose mean any fighter is one mistake from defeat. That volatility is exactly why upsets are the heartbeat of the sport — they reset rankings, mint new contenders, and remind everyone why the fights are still contested inside the cage rather than decided on paper. Browse the full ELO rankings to see where these giant-killers and the fighters they beat stand today, or explore more UFC statistics.