UFC 91: Couture vs. Lesnar was a mixed martial arts event held by the Ultimate Fighting Championship (UFC) on November 15, 2008 at the MGM Grand Garden Arena in Las Vegas, Nevada. The main event featured the return of UFC Heavyweight Champion Randy Couture versus Brock Lesnar in a title bout.

Matthew Riddle was forced to withdraw from his bout with Ryan Thomas due to an injury.Matt Brown was his replacement.

Amir Sadollah withdrew from his fight against Nick Catone due to a leg infection. A replacement for Sadollah could not be found, therefore the middleweight bout was scrubbed from the card. A welterweight match between Dustin Hazelett and Tamdan McCrory, previously scheduled for the preliminary card, was moved to the main card.

Unlike most UFC fight cards, every bout was aired on the PPV broadcast due to the speed of the main card bouts.

Fighters were awarded $60,000 bonuses.

The total payroll for the event was $1,118,000.

Brock Lesnar: $450,000 (includes $200,000 win bonus) def. Randy Couture: $250,000

Brock Edward Lesnar (/ˈlɛznər/; born July 12, 1977) is an American professional wrestler, actor, former mixed martial artist and amateur wrestler, signed with WWE and appearing on its Raw brand. He is also a former UFC Heavyweight Champion and former #1 ranked mixed martial arts (MMA) Heavyweight by Sherdog; he was ranked #5 before he announced his retirement at the end of 2011. Lesnar is an accomplished amateur wrestler, winning the 2000 NCAA heavyweight wrestling championship and placing second in 1999, losing in the finals to 1999 world freestyle wrestling champion and future New England Patriots offensive lineman Stephen Neal.

He gained prominence in World Wrestling Entertainment (WWE) from 2002 to 2004, where he is a former three-time WWE Champion, becoming the youngest WWE Champion at age 25 with his first reign. Lesnar was the 2002 King of the Ring and the winner of the 2003 Royal Rumble. After leaving WWE, Lesnar pursued a career in the NFL. He played during the preseason for the Minnesota Vikings, but ended up being a late cut. Lesnar returned to professional wrestling at the end of 2005, and joined New Japan Pro Wrestling (NJPW), where he won the IWGP Heavyweight Championship in his first match. He was officially stripped of the title by NJPW in July 2006, and took the physical belt with him to Inoki Genome Federation (IGF), where he was still recognized as IWGP Champion until June 2007.

Randy Duane Couture (pronounced /koʊˈtʊər/; born June 22, 1963) is an actor, retired American mixed martial artist, collegiate and Greco-Roman wrestler. During his tenures in the Ultimate Fighting Championship (UFC), Couture became a three-time UFC Heavyweight Champion, two-time UFC Light Heavyweight Champion, an Interim UFC Light Heavyweight Champion, and was the UFC 13 Heavyweight Tournament Winner. Couture is the first fighter to hold two UFC championship titles in two different divisions (heavyweight and light heavyweight). Couture has competed in a record 15 title fights. He holds the most title reigns in the UFC with five. His last fight with Lyoto Machida marked his 24th fight in the UFC, the third most amount of fights in the UFC (Tito Ortiz is first with 26 and Matt Hughes is second with 25). Couture is one of the first members of the UFC Hall of Fame. He is the only person over the age of 40 to have won a UFC championship fight, having done so four times.^{[citation needed]}

Couture was an Olympic wrestling alternate and has lived in Corvallis, Oregon, throughout much of his career, where he served as an assistant wrestling coach and a strength and conditioning coach for Oregon State University. He established Team Quest with Matt Lindland and Dan Henderson, a training camp for fighters, based out of Gresham, Oregon, and headed by coach Robert Folis. In 2005, Couture moved to Las Vegas, where he opened his own extensive chain of gyms under the name Xtreme Couture. He currently trains at his Las Vegas-based gym. Couture partnered with Bas Rutten in the opening of Legends Gym in Hollywood, California.

Curtis James Jackson III (born July 6, 1975), better known by his stage name 50 Cent, is an American rapper, entrepreneur, investor, record producer, and actor. He rose to fame with the release of his albums Get Rich or Die Tryin' (2003) and The Massacre (2005). His album Get Rich or Die Tryin' has been certified eight times platinum by the RIAA.

Born in the South Jamaica of Queens, New York City, Jackson began drug dealing at the age of twelve during the 1980s crack epidemic. After leaving drug dealing to pursue a rap career, he was shot at and struck by nine bullets during an incident in 2000. After releasing his album Guess Who's Back? in 2002, Jackson was discovered by rapper Eminem and signed to Interscope Records. With the help of Eminem and Dr. Dre, who produced his first major commercial successes, Jackson became one of the world's highest selling rappers. In 2003, he founded the record label G-Unit Records, which signed several successful rappers such as Young Buck, Lloyd Banks, and Tony Yayo.