5 biggest upsets in UFC history

#2. Amanda Nunes vs. Julianna Peña - UFC 269

UFC 269 saw Julianna Peña's upset of Amanda Nunes immediately enter the conversation as one of the most shocking victories in UFC history. Nunes is regarded as the greatest female fighter of all time and most felt this bout was going to be another easy victory for 'The Lioness'.

Nunes labeled Peña delusional for believing she would be able to pull off the upset. 'The Lioness' certainly seemed to be on the way to another victory after a strong showing in the first round. The second round, however, was a completely different story.

Peña rocked Nunes on the feet before locking in a rear-naked choke to win her first UFC championship. The result stunned fans everywhere and is easily the biggest upset of recent times.

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#1. Georges St-Pierre vs. Matt Serra - UFC 69

Georges St-Pierre is regarded by many as the sport's GOAT but it can't be forgotten that his legacy includes being on the receiving end of one of the most shocking moments in the company's history.

St-Pierre had only ever lost to Matt Hughes in his career and had finally righted that wrong in his last fight to become welterweight champion. Serra, on the other hand, had only managed a 5-4 record in his UFC career to that point.

In fact, Serra only earned the title shot thanks to winning season four of The Ultimate Fighter. In a change to the traditional TUF format, Serra's success earned him a guaranteed title shot which just happened to be against Georges St-Pierre.

With everything pointing towards a comfortable GSP victory, Serra pulled off arguably the biggest upset in UFC history when he knocked out the reigning champion in the very first round.

The combination of St-Pierre's greatness, Serra's lack of credentials at that point in his career and the nature of how Serra earned the opportunity all combined to make this arguably the greatest upset in the history of the UFC.