NXT TakeOver: Vengeance Day was a 2021 professional wrestling event produced by WWE. It was the 33rd NXT TakeOver, as well as the ninth Vengeance, and it took place on February 14, 2021, from the Capitol Wrestling Center, hosted at the WWE Performance Center in Orlando, Florida. The event aired via pay-per-view (PPV) and livestreaming, marking the first Vengeance to air on the WWE Network, and exclusively featured wrestlers from the promotion's NXT brand division. The event revived WWE's Vengeance PPV name, thus was the first Vengeance held since 2011. The event's name is also a play on Valentine's Day, as the event was held on the holiday. This was also the final NXT TakeOver event and only Vengeance to air on the American version of the WWE Network before it moved to Peacock in March. It was also the final Vengeance to air on PPV, as the following year's event was held as a television special. While the 2023 event returned to livestreaming, NXT's major events as of the 2022 calendar year no longer air on PPV.

Five matches were contested at the event. In the main event, Finn Bálor defeated Pete Dunne to retain the NXT Championship. In other prominent matches, MSK (Nash Carter and Wes Lee) defeated Grizzled Young Veterans (James Drake and Zack Gibson) to win the Men's Dusty Rhodes Tag Team Classic, while in the opening bout, Dakota Kai and Raquel González defeated Ember Moon and Shotzi Blackheart to win the inaugural Women's Dusty Rhodes Tag Team Classic. Vengeance Day also marked the WWE return of LA Knight, who previously performed as Slate Randall from 2013 to 2014 and was known as Eli Drake in Impact Wrestling.