A UFC Light Heavyweight Championship bout between current two-time champion Jon Jones and Thiago Santos served as the event headliner. A UFC Women's Bantamweight Championship bout between the current champion Amanda Nunes and former champion Holly Holm served as the event co-headliner. A bout between former UFC Heavyweight title challenger Francis Ngannou and former UFC Heavyweight ChampionJunior dos Santos was scheduled to take place at this event. The matchup was originally scheduled to take place in September 2017 at UFC 215, but dos Santos pulled out of that event, citing a failed drug test. However, it was reported on May 21, that the bout was being moved to headline UFC on ESPN 3 after former UFC Welterweight ChampionTyron Woodley was forced to pull out of his rematch against also former champion Robbie Lawler due to a hand injury. A featherweight bout between former Strikeforce and WEC Lightweight ChampionGilbert Melendez and Arnold Allen headlined the prelims of the event. The matchup was originally scheduled to take place in November 2018 at, however Melendez pulled out of the fight citing an injury. A bantamweight bout between bantamweight winner Alejandro Pérez and Yadong Song took place at this event. The matchup was originally scheduled to take place in March 2019 at UFC 235, but Song pulled out of the fight for undisclosed reasons. Sean O'Malley was expected to face Marlon Vera at the event. However, O'Malley announced his withdrawal from the bout on June 21 due a failed test for ostarine. The Nevada State Athletic Commission decided to suspend him due to the failed test, however the United States Anti Doping Association USADA will not impose any further sanctions. The ostarine in his system was likely residual from his previously failed test prior to UFC 229. Drako Rodriguez from King of the Cage was offered to replaced O'Malley initially; however the president of the promotion, Terry Trebilcock, refused to release him. Nohelin Hernandez served as the replacement. Melissa Gatto was scheduled to face Julia Avila at the event. However, Gatto was removed from the card on June 24 for undisclosed reasons and was replaced by returning veteran Pannie Kianzad. UFC 239 served as the first UFC to air on PPV in the United Kingdom. Following this event select UFC numbered events will now air on BT Sport Box Office in the United Kingdom
The following is the reported payout to the fighters as reported to the Nevada State Athletic Commission. It does not include sponsor money and also does not include the UFC's traditional "fight night" bonuses. The total disclosed payroll for the event was $3,331,000.
Jon Jones: $500,000 def. Thiago Santos: $350,000
Amanda Nunes: $500,000 def. Holly Holm: $300,000
Jorge Masvidal: $200,000 def. Ben Askren: $210,000
Jan Błachowicz: $92,000 def. Luke Rockhold: $200,000
Michael Chiesa: $104,000 def. Diego Sanchez: $103,000
Arnold Allen: $64,000 def. Gilbert Melendez: $200,000
