Which fighter defeated Conor McGregor at UFC 257 in 2021?

Dustin Poirier defeated Conor McGregor at UFC 257 in January 2021.

UFC 257 was held on January 23, 2021, at Etihad Arena on Yas Island in Abu Dhabi, United Arab Emirates. Poirier won the lightweight rematch by second-round technical knockout after stopping McGregor with punches and leg kicks.

The bout was a rematch of their 2014 featherweight contest, which McGregor had won by first-round knockout. The second meeting took place at lightweight and represented a major change in Poirier's career. By then, he had become one of the division's leading contenders and had challenged for the interim and undisputed lightweight championships.

UFC 257 was held during the promotion's “Fight Island” period amid the COVID-19 pandemic. The result gave Poirier a defining win and set up a trilogy fight with McGregor at UFC 264.