The Five Biggest Upsets in Women's UFC History, According to Our Elo Ratings

Julianna Peña over Amanda Nunes tops the 950 women's fights we measured. We compare the pre-fight Elo gap in five title changes that tore up the script.

Jorge E. GarcíaOctober 2, 20268 min read

An upset can be measured in several ways. Betting odds capture what the market expected. Fan memory measures the impact. Our Elo ratings ask a different question: how much competitive distance separated the winner and the loser right before they stepped into the Octagon?

By that standard, Julianna Peña over Amanda Nunes at UFC 269 is the biggest break from expectations in our women's database. Peña started the night at 1629.9 points and Nunes at 2299.5. The gap was 669.6 Elo points.

The full list reveals a pattern that is hard to ignore: all five of the biggest gaps ended in a new champion. Four were finishes. The fifth was a split decision. That does not prove women's MMA is more unpredictable; it does show how much an upset can be amplified when a dominant champion faces a challenger whose record is still worth far less to the model.

The short answer: Peña vs. Nunes was the biggest shock

These are the five wins with the largest pre-fight Elo gap across the four women's UFC divisions we have processed:

Julianna Peña vs. Amanda Nunes: a 669.6-point gap.
Alexa Grasso vs. Valentina Shevchenko: 497.1 points.
Holly Holm vs. Ronda Rousey: 476.5 points.
Rose Namajunas vs. Joanna Jędrzejczyk: 366.5 points.
Carla Esparza vs. Rose Namajunas: 358.0 points.

The order does not try to decide which result mattered most culturally. It does not reconstruct closing odds either. It simply compares the stored Elo rating of each fighter before the fight.

How to read the Elo numbers in this article

Our Elo ratings usually start at 1500 and summarize accumulated competitive value. As a rough guide, 1500–1699 means starting and developing; 1700–1799, an established fighter; 1800–1899, competitive elite; 1900–1999, contender elite; 2000–2199, proven elite; 2200–2399, title dominance; and 2400 or more, historic dominance.

The full explanation is in our guide to UFC Elo ratings. For this list we used a simple calculation: the favorite's rating minus the winner's rating. The bigger that gap, the bigger the break from what the competitive record suggested.

What we measure when we talk about an upset

The database contains 950 women's fights, from the division's UFC debut in February 2013 to the cutoff on September 12, 2026. There are 942 wins, plus draws and no contests. The lower-rated fighter won 378 times, but that figure includes tiny gaps that should not be called big upsets.

That is why the top five lives at the extremes. Only 21 women's wins came against a pre-fight gap wide enough for our current version to treat as a major upset in new fights. The list does not rewrite the past with that rule: it ranks the fights by the distance that already existed before they began.

1. Julianna Peña vs. Amanda Nunes: 669.6 points

Julianna Peña arrived at UFC 269 with a 1629.9 rating. Amanda Nunes sat at 2299.5, inside the title dominance band. No other result in our women's database pairs a champion that high with a winner that far down the scale.

Peña won by second-round submission. Our model added 212.4 points to her rating and took 94.4 from Nunes. The changes are not symmetrical because a title win boosts the winner's reward, while the loser's drop does not carry that boost. The criterion for this list, however, is the pre-fight gap: 669.6.

This is the difference between impact and measurement. Holm vs. Rousey usually sits at the center of historical lists because of its unforgettable image. Our Elo ranks Peña vs. Nunes higher because Nunes had built a much larger competitive lead before she lost.

2. Alexa Grasso vs. Valentina Shevchenko: 497.1 points

Alexa Grasso entered UFC 285 rated 1670.1. Valentina Shevchenko came in at 2167.2. The 497.1-point gap pitted a challenger still developing against a champion already established among the proven elite.

Grasso capitalized on a failed spinning attack from Shevchenko, took her back and locked in a fourth-round submission. The win earned her 205.7 points and cost the champion 91.4. The official result confirms the finish; the Elo explains why the title change was much more than a narrative surprise.

3. Holly Holm vs. Ronda Rousey: 476.5 points

Holly Holm was rated 1560.5 before UFC 193. Ronda Rousey arrived at 2037.0. The gap was 476.5 points.

Holm did not just win: she dismantled the champion's game and knocked her out with a second-round head kick. The UFC described it at the time as one of the biggest upsets in its history. Our records agree it was enormous, but place it third, because the gaps for Peña and Grasso were even larger.

The win lifted Holm by 203.5 points and dropped Rousey by 90.5. Once again, the title context amplified the new champion's reward.

4. Rose Namajunas vs. Joanna Jędrzejczyk: 366.5 points

Rose Namajunas started UFC 217 at 1636.0. Joanna Jędrzejczyk was defending the title at 2002.5. The gap was 366.5 points.

Namajunas won by first-round KO/TKO. The result added 189.8 points to her rating and took 84.3 from Jędrzejczyk. The later rematch confirmed the first win was no accident, but this list keeps the information available before the first fight: that is exactly what makes the result an upset.

5. Carla Esparza vs. Rose Namajunas: 358.0 points

Carla Esparza entered UFC 274 rated 1710.0. Namajunas was at 2068.0. The pre-fight gap was 358.0 points, just 8.5 fewer than in fourth place.

It is the only fight in the top five that went to the scorecards. Esparza won by split decision. Because it was a close decision, the performance weighed less than a finish would have: she gained 80.8 points and Namajunas lost 35.9. The size of the upset was huge even though the movement afterwards was smaller.

Why the top five are all title fights

The pattern has a reasonable explanation, though not a causal proof. A champion who stacks title defenses can climb far above the 1500 starting point. A challenger with a shorter UFC résumé can arrive with a noticeably lower rating. When the challenger wins, the pre-fight gap lands at the far end of the distribution.

That does not mean every title fight is unpredictable, or that a higher-rated champion is destined to fall. It means the biggest upsets need two conditions at once: a favorite who has built up a great deal of value and an opponent who wins before building a comparable rating.

It is also worth separating surprise from merit. The pre-fight Elo describes how unexpected the result was for the model. The actual win adds new information. After winning, each of these fighters stopped being the unknown she had been before.

What changes with the major-upset bonus

Since September 5, 2026, our current version adds a symmetrical bonus when a fighter beats a favorite rated well above her. The bonus grows with the gap and increases moderately when the win is dominant or comes inside the distance.

The rule does not change this top five. The list uses pre-fight ratings, and new versions do not broadly rewrite earlier history. Its purpose is to make future major upsets leave a stronger, zero-sum signal in the rankings.

Methodology and limitations

Query date: September 14, 2026. Sporting cutoff: September 12, 2026, the last fight processed. We analyzed 950 strawweight, flyweight, bantamweight and featherweight women's fights held between February 23, 2013 and the cutoff.

We included only wins in which the winner had a lower stored rating than the loser before the fight, and ranked them by the difference between the two. Draws and no contests were left out. Figures are rounded to one decimal place for readability.

Elo does not incorporate odds, public opinion, known injuries or later cultural impact. It is not a direct probability either. The men's history in our database does not yet have comparable retrospective coverage, so we do not use these numbers to claim these are the five biggest upsets in all of UFC history, or that women's MMA is more unpredictable.

Ratings and movements come from our internal database. Results, methods and title context were checked against the official UFC pages linked below.

Sources

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