Backlash is a recurring pay-per-view (PPV) and WWE Network event that was established by WWE in 1999. The event continued annually as the post-WrestleMania event until 2009, which was the final event until 2016. It was brought back that year following the reintroduction of the brand extension, where WWE again split its roster between the Raw and SmackDown brands where wrestlers are exclusively assigned to perform; the 2016 event also ended its previous tradition of being the post-WrestleMania pay-per-view. The event then continued annually until 2018 when it was replaced by Stomping Grounds the following year, but was reinstated in 2020. The 2021 Backlash was initially scheduled for June 20, however, during WrestleMania 37, it was revealed that Backlash would take place on May 16 and would be titled "WrestleMania Backlash," thus returning the event to its original position as the post-WrestleMania PPV, and being the first Backlash to have an altered title. It was the 16th event in the Backlash chronology and featured wrestlers from the Raw and SmackDown brands.