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.

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.

Royce Gracie (Portuguese: [ˈʁɔjsi ˈɡɾejsi], English: /ˈrɔɪs ˈgreɪsiː/; born December 12, 1966) is a Brazilian professional mixed martial artist, a UFC Hall of Famer and Brazilian Jiu-Jitsu practitioner. A legend and pioneer in the sport of mixed martial arts, he is widely considered to be the most influential figure in the history of modern MMA.

Gracie gained fame for his domination in the Ultimate Fighting Championship. He became known for beating opponents much larger than he was, and between 1993 and 1994, he was the tournament winner of UFC 1, UFC 2, UFC 4, and fought to a draw with Ken Shamrock in the championship match in the Superfight at UFC 5. Gracie popularized Brazilian Jiu-Jitsu and revolutionized mixed martial arts with his results contributing to the movement towards grappling and cross-training in the sport.

He holds the most submission victories in UFC history with 11, which he earned between UFC 1 and UFC 4.

Royce is a member of the Gracie family. He is the son of Hélio Gracie (Helio along with his older brother Carlos Gracie are the originators of Gracie Jiu-Jitsu—Modern Brazilian Jiu Jitsu) and spent his childhood in Rio de Janeiro, Brazil. As a toddler, Gracie learned Jiu-Jitsu from his father and his older brothers Rorion, Relson, and Rickson Gracie. He began competing at the age of 8 and by the time he was 16 had attained the level of blue belt.