The 2021 WrestleMania Backlash was the 16th Backlash professional wrestling pay-per-view (PPV) and livestreaming event produced by WWE. It was held for wrestlers from the promotion's Raw and SmackDown brand divisions. The event took place on May 16, 2021, from the WWE ThunderDome, hosted at the Yuengling Center in Tampa, Florida. It was WWE's first pay-per-view to present the ThunderDome from the Yuengling Center during the COVID-19 pandemic, following a four-month residency at Tropicana Field in St. Petersburg, Florida. It was also the first Backlash to livestream on Peacock. From 1999 to 2009, the concept of the Backlash pay-per-view was based around the backlash from WWE's flagship event, WrestleMania. The 2021 event returned Backlash to this original position as the post-WrestleMania pay-per-view, and it was in turn renamed to "WrestleMania Backlash" as it was based around the backlash from WrestleMania 37.

Seven matches were contested at the event, including one on the Kickoff pre-show. In the main event, Roman Reigns defeated Cesaro by technical submission to retain SmackDown's Universal Championship. In another prominent match, Bobby Lashley defeated Drew McIntyre and Braun Strowman in a triple threat match to retain Raw's WWE Championship. Also on the undercard, Bianca Belair defeated Bayley to retain the SmackDown Women's Championship and Rey Mysterio and Dominik Mysterio defeated Dolph Ziggler and Robert Roode to win the SmackDown Tag Team Championship, thus becoming the first-ever father and son team to hold a tag team championship in WWE.

The event received positive reviews from critics and fans. The event included a promotional tie-in for the zombie film Army of the Dead, which stars former WWE wrestler Batista. In addition to Batista doing a voiceover for the event's opening vignette, the Lumberjack match between Damian Priest and The Miz had the lumberjacks acting as zombies. This tie-in was heavily panned and covered in the media, with the New York Post calling it "one of WWE's saddest moments ever." Despite the negative criticism towards the tie-in, the rest of the event was well-received.