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.

Mark Munoz turned in a tremendous performance on Saturday at UFC 138, battering Chris Leben for two rounds before the fight was stopped prior to the start of the third. Munoz controlled the fight on the ground and opened up a big cut over Leben's left eye with hard right hands, and between the second and third rounds Leben's corner decided to stop the fight. After being awarded the victory by second-round technical knockout, Munoz said he wants the next shot at UFC middleweight champion Anderson Silva.

UFC 138: Leben vs. Muñoz Results

Preliminary card (Facebook)

Bantamweight bout: United States Chris Cariaso vs. England Vaughan Lee – Cariaso defeated Lee via split decision (28–29, 29–28, 29–28).

Welterweight bout: United States Chris Cope vs. England Che Mills – Mills defeated Cope via TKO (knees and punches) at 0:40 of round 1. This bout aired on the live broadcast and Spike broadcast following the Diabaté vs. Perosh fight.

Featherweight bout: Japan Michihiro Omigawa vs. England Jason Young – Omigawa defeated Young via unanimous decision (29–28, 29–28, 29–28).

Heavyweight bout: England Rob Broughton vs. England Phil De Fries – De Fries defeated Broughton via unanimous decision (29–28, 29–28, 29–28).

Welterweight bout: England John Maguire vs. United States Justin Edwards – Maguire defeated Edwards via unanimous decision (30–27, 30–27, 30–27). This bout aired last on the live broadcast following the Leben vs. Muñoz fight. This bout also aired on the Spike broadcast following the Alves vs. Abedi fight.

Main card

Lightweight bout: England Terry Etim vs. United States Edward Faaloloto – Etim defeated Faaloloto via submission (guillotine choke) at 0:17 of round 1.

Light Heavyweight bout: France Cyrille Diabaté vs. Australia Anthony Perosh – Perosh defeated Diabaté via submission (rear naked choke) at 3:09 of round 2.

Welterweight bout: Brazil Thiago Alves vs. Sweden Papy Abedi – Alves defeated Abedi via submission (rear naked choke) at 3:32 of round 1.

Bantamweight bout: England Brad Pickett vs. Brazil Renan Barão – Barão defeated Pickett via submission (rear naked choke) at 4:09 of round 1.

Middleweight bout: United States Chris Leben vs. United States Mark Muñoz – Muñoz defeated Leben via TKO (corner stoppage) at 5:00 of round 2.

UFC Fight Night 20 Results

 - Gray Maynard def. Nate Diaz via split decision (28-29, 30-27, 29-28)
 - Evan Dunham def. Efrain Escudero via submission (armbar) – Round 3, 1:59
 - Aaron Simpson def. Tom Lawlor via split decision (28-29, 29-28, 29-28)
 - Amir Sadollah def. Brad Blackburn via unanimous decision (30-27, 30-27, 30-27)
 - Chris Leben def. Jay Silva via unanimous decision (30-27, 30-27, 30-27)
 - Rick Story def. Jesse Lennox via split decision (30-27, 30-27, 29-28)
 - Thiago Tavares vs. Nik Lentz – majority draw (28-28, 28-28, 29-27)
 - Rory MacDonald def. Mike Guymon via submission (armbar) – Round 1, 4:27
 - Rafael dos Anjos def. Kyle Bradley via unanimous decision (30-27, 30-27, 30-27)
 - Gerald Harris def. John Salter via TKO (strikes) – Round 3, 3:24
 - Nick Catone def. Jesse Forbes via split decision (28-29, 29-28, 29-28)