|Promotion||Ultimate Fighting Championship|
|Date||July 11, 2009|
|Venue||Mandalay Bay Events Center|
|Attendance||10,871 (9,793 paid)|
The main event was a rematch between UFC Heavyweight Champion Brock Lesnar and Interim UFC Heavyweight Champion Frank Mir. This championship unification bout occurred as a result of former UFC Heavyweight Champion Randy Couture's year-long resignation from the promotion. During his absence, the UFC created an Interim championship, which Antonio Rodrigo Nogueira won by defeating Tim Sylvia. Nogueira and Mir were opposing coaches on The Ultimate Fighter: Team Nogueira vs Team Mir, and fought for the interim championship at UFC 92. During the airing of the television program, Couture returned to the company and UFC President Dana White announced he would defend the title against Lesnar at UFC 91. The winners of the Couture vs Lesnar and Nogueira vs Mir matches would fight for the undisputed title. In his fourth professional fight, Lesnar defeated Couture via technical knockout to become the UFC Heavyweight Champion. Mir was crowned interim champion after becoming the first fighter to finish Nogueira. The match between Lesnar and Mir was set for UFC 98. However, Mir injured his knee while training, and withdrew from the bout. The next day, it was announced the fight would be moved to UFC 100. Lesnar and Mir had fought once before, at UFC 81 (Lesnar's UFC debut); Mir won via kneebar submission.
The co-main event featured Georges St-Pierre, defending the Welterweight Championship against Thiago Alves. Alves entered the fight after consecutive victories over three top UFC welterweights: Josh Koscheck, Matt Hughes and Karo Parisyan. St-Pierre had previously defended the title against Jon Fitch and UFC Lighweight Champion BJ Penn.
The third match on the main card was between top middleweight contenders Dan Henderson and Michael Bisping. The two were opposing coaches on the ninth season of The Ultimate Fighter (Henderson on Team USA and Bisping on Team UK). Bisping had a professional MMA record of 18–1, and was undefeated since moving to middleweight. He entered the bout following wins over Charles McCarthy, Jason Day and Chris Leben. On June 2, it was announced the winner of the fight would get a shot at UFC Middleweight Champion Anderson Silva.
- Gugerty defeated Grice via submission (guillotine choke) at 2:36 of round 1.
- Lawlor defeated Dollaway via submission (guillotine choke) at 0:55 of round 1.
- Kim defeated Grant via unanimous decision (30–26, 30–26, 30–26).
- Miller defeated Danzig via unanimous decision (30–27, 30–27, 30–27).
- Jones defeated O'Brien via submission (modified guillotine choke) at 2:43 of round 2.
- Coleman defeated Bonnar via unanimous decision (29–28, 29–28, 29–28).
- Akiyama defeated Belcher via split decision (30–27, 28–29, 29–28).
- Fitch defeated Thiago via unanimous decision (30–27, 29–28, 29–28). This fight was delayed until after the main event due to time constraints.
- Henderson defeated Bisping via KO (punch) at 3.20 of round 2.
- St-Pierre defeated Alves via unanimous decision (50–45, 50–44, 50–45)
- Lesnar defeated Mir via TKO (punches) at 1:48 of round 2
Fighters were awarded $100,000 bonuses.
- Fight of the Night: Yoshihiro Akiyama vs. Alan Belcher
- Knockout of the Night: Dan Henderson
- Submission of the Night: Tom Lawlor
- Brock Lesnar: $400,000 (no win bonus) def. Frank Mir: $45,000
- Georges St-Pierre: $400,000 ($200,000 win bonus) def. Thiago Alves: $60,000
- Jon Fitch: $90,000 (includes $45,000 win bonus) def. Paulo Thiago: $8,000
- Dan Henderson: $250,000 ($150,000 win bonus) def. Michael Bisping: $150,000
- Yoshihiro Akiyama: $60,000 ($20,000 win bonus) def. Alan Belcher: $19,000
- Mark Coleman: $100,000 ($50,000 win bonus) def. Stephan Bonnar: $25,000
- Jim Miller: $22,000 ($11,000 win bonus) def. Mac Danzig: $20,000
- Jon Jones: $18,000 ($9,000 win bonus) def. Jake O'Brien: $13,000
- Dong Hyun Kim: $58,000 ($29,000 win bonus) def. T.J. Grant: $5,000
- Tom Lawlor: $16,000 ($8,000 win bonus) def. C.B. Dollaway: $14,000
- Shannon Gugerty: $10,000 ($5,000 win bonus) def. Matt Grice: $7,000
- "UFC 100 draws live gate of $2,128,490". Five Ounces of Pain. July 21, 2009. Retrieved 2009-07-21.
- Iole, Kevin. "Couture returns to UFC, faces Lesnar – MMA – Yahoo! Canada Sports". Ca.sports.yahoo.com. Retrieved 2009-05-15.
- Iole, Kevin. "Lesnar drops Couture for UFC heavyweight crown – MMA – Yahoo! Sports". Sports.yahoo.com. Retrieved 2009-05-15.
- Sievert, Steve (2009-01-05). "Sizing up Brock Lesnar vs. Frank Mir II". MMAjunkie.com. Retrieved 2009-05-15.
- "Injury to Frank Mir forces cancellation of UFC 98 rematch vs. Brock Lesnar". Five Ounces of Pain. 2009-03-06. Retrieved 2009-05-15.
- Meltzer, Dave. "UFC moves Lesnar-Mir to UFC 100 – MMA – Yahoo! Canada Sports". Ca.sports.yahoo.com. Retrieved 2009-05-15.
- "UFC 81 Play-by-Play". Sherdog.com. Retrieved 2009-05-15.
- "Fight Finder – Thiago "Pitbull" Alves's Mixed Martial Arts Statistics". Sherdog.com. Retrieved 2009-05-15.
- Stupp, Dann (2009-06-02). "Winner of UFC 100's Michael Bisping vs. Dan Henderson fight gets a title shot". MMAjunkie.com. Retrieved 2009-07-13.
- "Fight Finder – Michael "The Count" Bisping's Mixed Martial Arts Statistics". Sherdog.com. Retrieved 2009-05-15.
- "State Of Nevada" (PDF). Retrieved 2009-08-19.
- Fitch vs Thiago, last match of live coverage
- ic: interim champion
- "UFC 100 Bonuses and Award for 'Lesnar vs. Mir' PPV Fights". MMAmania. 2009-07-12. Retrieved 2009-07-12.[dead link]
- "UFC 100 fighters salaries: Lesnar and St. Pierre get top paydays in $1.8 million payroll". MMAjunkie.com. Retrieved 2009-07-13.