Dec. 11, 2021 was one of the most shocking days in MMA history.

At UFC 269, Julianna Peña pulled off one of the biggest, if not the biggest, upsets in history when she stopped all-time great Amanda Nunes and took her UFC women's bantamweight crown. Nunes entered the fight on a 12-fight winning streak, a run that spanned six years and eliminated any debate on who's the greatest pound-for-pound female fighter in MMA history. Few expected Peña to win, yet she marched forward and out-slugged the Brazilian to eventually lock in a submission.

You can rewatch Peña's huge upset win in the video above.

Peña (13-5 MMA, 8-3 UFC) returns to the octagon Saturday in the co-main event of UFC 316 (pay-per-view, ESPN, ESPN+) at Prudential Center in Newark, N.J. She starts her second title reign with an attempted defense against two-time Olympic gold medalist and two-time PFL champion Kayla Harrison (18-1 MMA, 2-0 UFC), who is a massive favorite as the challenger to win the belt.

This article originally appeared on MMA Junkie: UFC 269 full fight video: Julianna Peña vs. Amanda Nunes 1

MMA Mixed Martial Arts News, Photos, Stats, Scores, Schedule & Videos