UFC 138: Leben vs. Muñoz was a mixed martial arts event held by the Ultimate Fighting Championship on November 5, 2011 at LG Arena in Birmingham, England. The event aired on the same day, via tape delay, on Spike TV in the U.S. and live on Sportsnet in Canada. The event was the second that the UFC has hosted in Birmingham, the first was UFC 89 back in 2008 also featuring Chris Leben in the main event.

After several tenatively scheduled 2011 events at various locations around the United Kingdom did not materialize, including Glasgow, Liverpool, London as well as a planned return to Ireland, it was expected that the organization would not hold an event in the area during 2011.

The main event was the first non-title five round fight in the history of the UFC.

Mark Scanlon was expected to face James Head at this event. However, Scanlon was pulled from the bout and replaced by promotional newcomer John Maguire Then, on September 28, Head himself pulled out of the fight due to an undisclosed injury and was replaced by Justin Edwards.

Christian Cyrus Leben (born July 21, 1980) is an American mixed martial artist currently signed to the Ultimate Fighting Championship where he fights as a middleweight. Leben first appeared in the inaugural season of The Ultimate Fighter reality series. He began his UFC career with five victories in a row before suffering a knockout loss to current champion Anderson Silva. He has won bouts over Wanderlei Silva, Yoshihiro Akiyama, Jorge Santiago, Mike Swick, Jorge Rivera, Patrick Côté, and Alessio Sakara. Leben is currently ranked as the #10 middleweight fighter in the world by MMAWeekly.

Once, visiting his brother at work, Leben noticed an MMA gym located across the street, home to Team Quest. Trainer Robert Follis accepted Leben into the team, and soon Leben was training with Randy Couture, Matt Lindland, Nate Quarry, and Ed Herman. After refining his talent, Leben began fighting as an amateur, achieving a record of 5–0, and capturing the FCFF and UFCF middleweight titles.

After his success in the amateur ranks, Leben turned professional. He won his first five fights, three of them by knockout, and in the process won the Gladiator Challenge, Sportfight, and WEC middleweight titles. Leben achieved wins against Benji Radach, Mike Swick, Jorge Rivera, Edwin Dewees and Patrick Cote, an otherwise perfect record blemished only by a decision loss to Joe Doerksen.

Thiago Alves d'Araujo (Portuguese pronunciation: [tʃiˈaɡu ˈawvis]; born October 3, 1983) is a Brazilian mixed martial artist currently competing as a welterweight in the Ultimate Fighting Championship. He started training in Muay Thai when he was 15 and mixed martial arts at 17. He is a brown belt in Brazilian Jiu-Jitsu and has been described as a "Muay Thai wrecking machine".

After beginning his fight training at the age of 14, Alves won his first professional bout at just 15 years old, defeating a 25-year-old by unanimous decision. At 19, Thiago relocated from Brazil to Coconut Creek, Florida to train full-time at the prestigious American Top Team camp.

After beginning his career in smaller organizations such as the Ironheart Crown, Absolute Fighting Championships and King of the Cage, Alves, with a record of 8–3, received an invitation to make his UFC debut at Ultimate Fight Night 2 against fellow UFC newcomer Spencer Fisher, The fight would take place on Alves' twenty-second birthday.

Brad Pickett (born September 24, 1978) is an English mixed martial artist and the former Cage Rage British Featherweight champion and UCMMA Featherweight Champion. He currently competes as a Bantamweight in the Ultimate Fighting Championship. As of October 2011, Pickett is ranked the #8 bantamweight in the world by Sherdog.Dana White and Mike Goldberg have stated that Pickett is one of their favourite fighters to watch due to his crowd pleasing style of fighting.

Brad's nickname and his flamboyant entrance to the ring are not derived from Brad Pitt's character "One Punch Mickey" from the movie Snatch but from his grandfather.^{[citation needed]} His unique entrance sees him entering to the song "Wallop" by Chas & Dave, wearing a string vest, cutoff jeans and his customary trilby hat.^{[citation needed]} He is a supporter of the London football club Tottenham Hotspur.

He has fought mainly for the Cage Rage organization. Pickett's first appearance was on 27 November 2004 with a win over Stuart Grant. Pickett became the British Cage Rage Featherweight Champion on 10 September 2005 at Cage Rage 13 by defeating Ozzy Haluk via submision following a flying footstomp to the face. Pickett later lost the belt to the tough Robbie Olivier by rear naked choke in round 3. He is the former UCMMA Featherweight champion.

Dana White (born July 28, 1969) is the current President of the Ultimate Fighting Championship (UFC), a mixed martial arts organization based in the United States.

Born in Manchester, Connecticut on July 28, 1969, White grew up in Las Vegas, Nevada, Ware, Massachusetts and Levant, Maine. White is a passionate Boston Red Sox fan. During his youth, he bounced back and forth between Boston and Maine. He attended the University of Massachusetts Boston but did not finish; however, while there he did launch a boxing program for inner-city youth.

White has a background as an aerobics instructor. In 1992, White established Dana White Enterprises in Las Vegas. He conducted aerobics classes at three gyms in the Las Vegas area and began managing MMA fighters Tito Ortiz and Chuck Liddell.

While working as a manager, White learned that Semaphore Entertainment Group, the parent company of the UFC, was looking for a buyer for the UFC. White contacted childhood friend Lorenzo Fertitta, an executive at Station Casinos, and a former commissioner of the Nevada State Athletic Commission. Within a month, Lorenzo and his older brother Frank bought the UFC, with White installed as its president. White currently owns about 9% of Zuffa, LLC, the entity the Fertitta brothers created to own and manage the UFC.