The 2018 All In was the inaugural All In and was an independent professional wrestling pay-per-view (PPV) event promoted by Cody Rhodes and The Young Bucks (Matt Jackson and Nick Jackson) in association with Ring of Honor (ROH). At the time, Rhodes and the Jacksons had been a part of the Bullet Club of New Japan Pro-Wrestling (NJPW) and ROH. The event took place during Labor Day weekend on Saturday, September 1, 2018, at the Sears Centre Arena in the Chicago suburb of Hoffman Estates, Illinois. The event aired live on traditional PPV outlets, FITE TV, and Honor Club, but it was later made available for on-demand viewing on the NJPW World streaming service. The event included Zero Hour, an hour-long pre-show that aired on WGN America. While independently produced, the event featured wrestlers from NJPW, Impact Wrestling, Lucha Libre AAA Worldwide (AAA), Major League Wrestling (MLW), and the National Wrestling Alliance (NWA).

The event had 11 matches, with two being on the pre-show. The show's main event was a six-man tag team match which saw The Golden Elite (Kota Ibushi, Matt Jackson, and Nick Jackson) defeat Rey Fénix, Bandido, and Rey Mysterio. In the penultimate match, Kazuchika Okada defeated Marty Scurll. On the undercard, Cody defeated Nick Aldis to win the NWA Worlds Heavyweight Championship, Jay Lethal successfully defended the ROH World Championship against Flip Gordon, and IWGP Heavyweight Champion Kenny Omega defeated Penta El Zero in a non-title match.

The event was notable for being the first non-WWE or World Championship Wrestling (WCW) promoted professional wrestling event in the United States to sell 10,000 tickets since 1993. The success of the event inspired the formation of All Elite Wrestling (AEW) in January 2019, with The Elite (Rhodes, the Jacksons, and Omega) becoming executive vice presidents of the company. AEW would subsequently establish a spiritual successor to All In entitled All Out, which is also held during Labor Day weekend and considered one of AEW's "big four" annual PPV events. In 2023, AEW adopted the "All In" name for a PPV held at Wembley Stadium in London, England, referred to as All In London, which was the promotion's United Kingdom debut held during the August Bank Holiday weekend, with AEW to return for the event in 2024.