The 2021 All Out was the third annual All Out professional wrestling pay-per-view (PPV) event produced by All Elite Wrestling (AEW). It took place during Labor Day weekend on September 5, 2021, at the Now Arena in the Chicago suburb of Hoffman Estates, Illinois. It was the first All Out event to be held on a Sunday. It was also AEW's first pay-per-view held outside of Daily's Place in Jacksonville, Florida since the start of the COVID-19 pandemic in March 2020. The event aired through traditional PPV providers, as well as on B/R Live in North America and FITE TV internationally.

Ten matches were contested at the event, including one on the Buy In pre-show. In the main event, Kenny Omega defeated Christian Cage to retain the AEW World Championship. In other prominent matches, CM Punk defeated Darby Allin

(which was also Punk's AEW debut match and Punk's first professional wrestling match in seven years); Chris Jericho defeated MJF in a career threatening match; Lucha Brothers (Penta El Zero Miedo and Rey Fénix) defeated The Young Bucks (Matt Jackson and Nick Jackson) in a steel cage match to win the AEW World Tag Team Championship; Dr. Britt Baker, D.M.D. defeated Kris Statlander to retain the AEW Women's World Championship; and Miro defeated Eddie Kingston to retain the AEW TNT Championship in the opening bout. The event also saw the AEW debuts of Minoru Suzuki, Adam Cole, Ruby Soho (who won the women's Casino Battle Royale), and Bryan Danielson.

Tickets for All Out sold out within a day, and the event was attended by over 10,000 people. It also received over 200,000 pay-per-view buys, making it the most bought non-WWE professional wrestling PPV event since 1999.

All Out received critical acclaim, particularly for the cage match and the newsworthy surprise debuts, and was also highly rated by fans. Since its initial airing, All Out has been hailed as one of the greatest wrestling pay-per-views of all time.