UFC 125: Resolution was a mixed martial arts event held by the Ultimate Fighting Championship on January 1, 2011 at the MGM Grand Garden Arena in Las Vegas, Nevada, United States.

The planned rematch between UFC Middleweight Champion Anderson Silva and Chael Sonnen from their UFC 117 bout was at one point thought to take place at this event.

On October 26, 2010, Shane Carwin had to pull out of his fight with Roy Nelson due to a back injury that required surgery. Nelson was then pulled from the card altogether.

On October 28, 2010, UFC president Dana White announced that World Extreme Cagefighting (WEC) would merge with the UFC and that WEC Featherweight Champion Jose Aldo would be promoted to UFC Featherweight Champion.Josh Grispi was pulled from a planned WEC 52 bout with Erik Koch to challenge Aldo for the Featherweight title at this event. However, Aldo was later forced off the card with an injury. Grispi remained on the card and fought Dustin Poirier.

A lightweight bout between Cole Miller and Matt Wiman, which was originally scheduled to take place at this event, was moved to UFC: Fight For The Troops 2.

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.

Frank James Edgar (born October 16, 1981) is an American mixed martial artist, who competes as a lightweight in the Ultimate Fighting Championship and is a former UFC Lightweight Champion. His first career loss came against Gray Maynard in 2008, which marked the beginning of a noted rivalry. He later avenged the loss to Maynard with a KO victory in 2011. As of March 2012, he is ranked as the #2 lightweight in the world by Sherdog.com.

Born and raised in Toms River, New Jersey, Frankie Edgar wrestled at Toms River High School East, making it to the New Jersey state championship tournament on three occasions, placing second as a junior and fifth as a senior. Edgar is the oldest of 3 children, Edgar went on to compete in the NHSCA Senior Nationals and placed second before he finished high school. He continued wrestling at Clarion University of Pennsylvania, where he qualified for the nationals all four years there. Edgar is also an assistant coach for the Rutgers University wrestling team.

Edgar entered his first mixed martial arts fight with only a few weeks of training outside of his wrestling background. Edgar originally trained with Rob Guarino of Rhino Fight Team, but today he is part of the Gracie system under Ricardo Almeida in Hamilton, NJ. Since seventh grade Edgar has wrestled with Steve Rivera at Elite Wrestling NJ in Jackson, NJ. His boxing trainer is Mark Henry of Millstone, NJ.

Bradley Gray Maynard (born May 9, 1979) is an American amateur wrestler and professional mixed martial artist, who competes as a lightweight in the Ultimate Fighting Championship. He has recorded one of the fastest knockouts in UFC history, at 9 seconds against Joe Veres. He is one of only two fighters to hold a win over former champion Frankie Edgar, with whom he has a noted rivalry. As of March 2012, Maynard is ranked as the #4 lightweight fighter in the world by Sherdog.

Maynard's father, Jan, was a two-time Ohio high school state wrestling champion. He also has a sister named Misty. Maynard attended Bonanza High School in Las Vegas and transferred to St. Edward High School in Lakewood, Ohio, for two years, and excelled in its wrestling program. In 1997, he placed second in the Ohio High School Athletic Association (OHSAA) state tournament in the 140 lb weight class for Division I. In 1998, he was the state champion at the 152 lb weight class. His high school record was an impressive 135–16, including being undefeated in his sophomore and senior years. His nickname of "Bully" came from his dog, Hank, a bull terrier he rescued.

Philip George Baroni (born April 16, 1976) is an American mixed martial artist. He has a professional MMA record of 14–14–0. Baroni has fought in the Ultimate Fighting Championship (UFC) where he holds a record of 3–7–0. Also he has fought in the PRIDE FC where he holds a record of 4–2–0. He has developed a reputation for his boxing ability and knockout power, although he is an accomplished wrestler as well. He formerly trained with Team Hammer House, whose members include two PRIDE fighters and former UFC heavyweight champions, Mark Coleman and Kevin Randleman.

Baroni grew up in Massapequa Park, Long Island, New York. He was expelled from Massapequa High school for assaulting a janitor at the school. Baroni attended Hofstra University before transferring to Central Michigan University, where he was a double major in biology and psychology, and earned his degree in psychology. He was also an amateur bodybuilder from the age of 17 to 20, competing in six shows in which he placed either first or second. He studied kickboxing under Keith Trimble, and had seven kickboxing matches, winning all by knock out. He also competed in 10 amateur boxing matches, also winning all 10 by knock out. Although Baroni was a fan of UFC, he did not want to compete in it until the organization had implemented weight classes.^{[citation needed]}